12
GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT BY SARAH B. HOLT Qaltan LQboratory INTBODUCTION For determining methodR of inheritance in man data from parents and children, sibs and twins am necessary sources of information. In a previous paper (Holt, 1962) finger ridge-count data from all these types of relatives were analysed. Now additional data for parenta and children are available, and the present paper is devoted to a further consideration of the relationship between parents and children for total ridge-count. Although total ridge-count is a discontinuous character, it behaves very like a continuously varying one. The theoretical correlation between parents and children for a mefrioal oharaoter is 0.6 when additive genes with independent effect, but without dominance, are pweent (Fisher, 1918). Moreover, the theoretical coe5cient of correlation between the measurement of the child and the midparent measurement (i.e. the average value for the two parenta, firat used by Galton, 1889) is 1/42, or 0.71, under thew conditions (me Penrose, 1949). Penroee hae also pointed out that with suitable data the regression of offsprhg on the average value for the parents is a means of detecting recessivity Linear -ion suggeete laok of dominrmoe and the p m n c e of additive genes, while deviations from linearity are aseociatd with dominance or receesivity, ~~ccording to the direction of the divergence. Calculations have been made on total ridge-count data from fifty British familiea (Holt, 1962), and it wtw found that the parent-child correlation ooe5cient was not sigdioantly Merent fmm 0.6, while the midparent-child correlation was in good agreement with the theoretiad value for absence of dominance. The regreasion for total ridge-count of offspring on midparent value waa linear, the value of the regression coefficient being 0.924. Thus it appeared that total ridge-count is due to a number of additive genes and that there is no dominance. "he data available for these calculations were, however, small, and correlations between mother and son, mother and daughter, father and son, and father and daughter were each baaed on as few as fiftythree pairs. During the paat few years the fingerprints of a further 100 families (consisting of both parente and at least one child) have been collected, and the total ridge-count ascertained for each individual. In the present paper correlations for the total ridge-count between parent and child, mother and child, and father and child in t h e 100 families are given. In addition, previous calculations have been repeated using all the data now available. Some resulta obtained for 83 of the 100 new families were reported briefly in a paper given at the Ninth International Con- of Genetics (Holt, 1966). Some unusual fingerprint patterns were found in some of the familiea. Descriptions of those of intereet from the point of view of ridge-counting, together with the methoda of aamrtaining the counts, were given in an earlier paper (Holt, 1965).

GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

Embed Size (px)

Citation preview

Page 1: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

BY SARAH B. HOLT Qaltan LQboratory

INTBODUCTION For determining methodR of inheritance in man data from parents and children, sibs and twins am necessary sources of information. In a previous paper (Holt, 1962) finger ridge-count data from all these types of relatives were analysed. Now additional data for parenta and children are available, and the present paper is devoted to a further consideration of the relationship between parents and children for total ridge-count.

Although total ridge-count is a discontinuous character, it behaves very like a continuously varying one. The theoretical correlation between parents and children for a mefrioal oharaoter is 0.6 when additive genes with independent effect, but without dominance, are pweent (Fisher, 1918). Moreover, the theoretical coe5cient of correlation between the measurement of the child and the midparent measurement (i.e. the average value for the two parenta, firat used by Galton, 1889) is 1/42, or 0.71, under thew conditions (me Penrose, 1949). Penroee hae also pointed out that with suitable data the regression of offsprhg on the average value for the parents is a means of detecting recessivity Linear -ion suggeete laok of dominrmoe and the p m n c e of additive genes, while deviations from linearity are aseociatd with dominance or receesivity, ~~ccording to the direction of the divergence.

Calculations have been made on total ridge-count data from fifty British familiea (Holt, 1962), and it wtw found that the parent-child correlation ooe5cient was not sigdioantly Merent fmm 0.6, while the midparent-child correlation was in good agreement with the theoretiad value for absence of dominance. The regreasion for total ridge-count of offspring on midparent value waa linear, the value of the regression coefficient being 0.924. Thus it appeared that total ridge-count is due to a number of additive genes and that there is no dominance. "he data available for these calculations were, however, small, and correlations between mother and son, mother and daughter, father and son, and father and daughter were each baaed on as few as fiftythree pairs.

During the paat few years the fingerprints of a further 100 families (consisting of both parente and at least one child) have been collected, and the total ridge-count ascertained for each individual. In the present paper correlations for the total ridge-count between parent and child, mother and child, and father and child in t h e 100 families are given. In addition, previous calculations have been repeated using all the data now available. Some resulta obtained for 83 of the 100 new families were reported briefly in a paper given at the Ninth International Con- of Genetics (Holt, 1966).

Some unusual fingerprint patterns were found in some of the familiea. Descriptions of those of intereet from the point of view of ridge-counting, together with the methoda of aamrtaining the counts, were given in an earlier paper (Holt, 1965).

Page 2: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

SARAH B. HOLT

No. of families

47 25 I 9

5 3 I

1 0 0

27 1

Maleb Females Total children

24 23 47 29 21 5 0 27 30 57 16 4 20

6 9 1 5

2 4 6

104 9 1 I 9 5

MATEBIAL UBED

"he new eample ia made up from 100 British familiea includmg ten Jewieh ones. The majority of the familiea were resident in or near London, but some were from other pmta of the country. A group of twenty-three (of which twenty-one were Weleh) lived in a village in Montgomery- shire. Thirty-one of the familiea fingerprinted were those of children attending a Hertfordshire school. The total number of children in the sample is 196 (104 males and 91 females). Children of the Welsh families number 63 (26 males and 27 females), while those in the other non-Jewiah families number 118 (64 males and 54 femalea). Of the 24 children of the Jewiah families, 14 are malea and 10 females. Neither in the Welsh nor Jewish familiea waa there any distinctive Merence from the remaining familiea in total ridge-count distribution. No clusterine, was noticeable in correlation tables in either me.

The size and composition of the families are shown in Tables 1 and 2.

Table 1. Compo8ition of families in sample ~~~~

Campition of family

Melee

I

0

2 I 0

3 2 I 0

4

4

2

I

2

Females

0

I

0

I

2

0 I

2

3 0 2

I

4 4

Total children

1

I

2 2 2

3 3 3 3

4 4

5 5 6

No. of families

24 23

7 I 5 3

6 9

3

2

2

2

I

2

I

Table 2. Proportion of malea an& females in familiea of different Biz

No. of children in family

Families of I Femilies of 2 Familiee of 3 Familiee of 4 Familiee of 5 Families of 6

Total

The total ridge-comb of p m n b and children were given in the Appendix to an earlier paper (Holt, 1955). In Table 6 of the Appendix the 96 families begmnmg from the fiftieth were used.

Page 3: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

27 2 G E N E T I C S OF DERMAL R I D G E S

The first three families with both parents under the heading ‘Related families’, and the last family under ‘Families with only one parent counted’, were also included. The father of this last family had lost digit left \’ in an accident. Hie total ridge-count was estimated to be 171.

a consequence of the method of sampling. Prints of the parents, and in one caae of two sibs, were taken, as in each caw a child attended the Hertfordshire school; they were not taken because the families were related. Other related families have been omitted and, as far as is known-and inquiries were made in each caae- none of the other families used are related in any way.

Among the families printed when the data were being assembled were six with twins. Two of these families had no other children and were therefore not used. In the other four only the ridge-counts of the single-born children were used. One family included two pairs of twins, one dizygotic and the other apparently monozygotic. The total ridge-counts of the members of these six families are given in Table 3.

The three related families were included

,... - . .

~ 69 I 74 i

Table 3. Total ri&e-cou?tts of families containing twins

I

2

_ _ _ . - -

(M. 82, F. I 17 ) twins, F. 77, (M. 1279 M. 155) twins F. 16, M. 137, (F. 91. F. 102) twins

The total ridge-counts for both parents and children in the new sample fall within the range 0-280; fathers 18-273, mothers 1-268, sons 0-262 and daughters 0-234. The mean ridge-counts for fathers and mothers are 144.53 (a= 55.169) and 130.23 (a= 51.064) respectively. Sons have a mean of 155.10 (a= 50.247) and daughters of 124.51 (a= 53-278). These values can be com- pared with the mean ridge-counts and standard deviations of a population sample of 825 males and 825 females (in which these families were also included) (Holt, 1955), viz. 144.98 (a= 51.0’79) for males and 127.23 (a=52.507) for females. Fathers have a rather higher variance than mothers, the reverse of the situation for the two sexes in the general population. The mean ridge-count for sons is higher, though not significantly so, than either the mean for fathers or the mean for males in the population sample. This is probably a chance effect.

Data from the first sample of 50 families have been used in this paper combined with the new data. It should be noted, however, that some amendments have been made. The ridge-counts of twin6 (one pair of male and one of female) have been omitted, and those of four other children added (one male and three females). As the pair of male twins had no sib, the number of families is reduced to 40 and, although the alteration8 have left the total number of children unaltered, there are now 52 males and 54 females in this sample.

The total ridge-counts of the 50 families in the first sample were given in Table 17 of a previous paper (Holt, 1952). In the third family two daughters, with total ridge-counts 162 and 190, have been added. The twenty-sixth family has been omitted (twins with no sib). One daughter, with total ridge-count 20, has been added to the fortieth family, while the twins have

Page 4: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

SARAH B. HOLT 273

ridge count

of parsnt

60-279 $0159 -39 ocnI9

--

80-199 6-79 40-159 -139 -119

8 - 9 9 2 -9 -59 -39 -19

Total --

been omitted from the forty-third family, and a son, with ridge-count 11 1, has been added to the fiftieth family.

The additional data used in Tables 8, 9 and 10 (see also Table 12) m given in Table 6 of the Appendix referred to earlier, under ‘Families with only one parent counted’. Thirteen of these families were uaed, i.e. aU exoept the first and the last.

- *1q

- - - I - 1 - I

3

I

3 - -

12

NOTE ON STATISTICAL METRODS USED

Correlations and standard errore have been calculated according to the usual formulae, aa if all pairs of values were independent. This is not strictly true, except for interparental correlationa, since parent-child paire from a aingle family with more than one child are not independent. Unfortunately, the neoeaaary correotiona have not yet been worked out. However, dthough the results obtained from the usual formulae may be inaccurate, there is no -on to believe that they are groeely misleading. In Tables 4 and 6, used for calculating parent-ohild correlation, eaoh ohild haa been entered

twice, onoe with esoh parent. Owing to the uae of this method of compiling the tablee, the standard errora of the correlations calculated by the usual formula are even more inwourate. Hence no standard error is given in them two ~8888.

160-179

- - I

4 10

13 6 4

4

a

3

I 1

2

-

60

PABENT-CHILD OOEBEL~TION IN 100 NEW F-

The distribution of total ridge-count in parents and ohildmn in the new familiea is shown in Table 4, in the form of a correlation table with grouping interval 20. The value of the parent- child correlation coefficient, r, is 0-46. The parent-parent correlation, r = 0.03 f 0.10, is not s w c c m t .

180-199 -19 --- a 3

I 5 3 I

I1 8 4 16

3 3 5 a a I I 3

I I

- I

I -

- - - - ---

46 3s

Table 4. Daetribution of tdal tidge-wunt in wren& and children of 100 fami lk (actual canfa) -

Total Tohl xidgwmmt of child

6079 1-139 140-159 -59

- - - a 4 7 2 5 5 a 7 I - I

6 3 8 I9

73 39 53 50 3’

1s 4 5

c

38

a2 36 36 58 50 18 2 a 390

r=045.

Except in the above inatanca and for the caloulation of midparent-ohild correlationa and regreaaiona, a aex correction hes been wed throughout. Thie seemed an appropriate way of combining data for mdea and females. A value equal to the Werenoe in means between the

18 Val. 20

Page 5: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

274 (;EKETICS O F DERMAL RIDGES

sexea in a population sample (see Holt, 1955) has been added to the total ridge-count of each female. For convenience the difference has been taken to the nearest whole number, i.e. 18.

The value of the parent-child correlation for the sample remains unaltered when the sex correction is used, while the value of the parent-parent correlation is slightly reduced, r = 0.02 0.10. The mother-child correlation is 0.42 +_ 0.06 and the father-child correlation 0.49 5 0.05. There is, therefore, agreement between the first and second samples in showing no maternal effect. Parent-child and mother-child correlations are rather lower than would have been expected from the monozygotic twin-twin correlation ( r =0.95 f 0.02; see Holt, 1952), but, on the other hand, the values for the first sample were high by thh criterion, though not significantly different from 0.5.

PARENT-CHILD CORRELATIONS ESTIMATED FROM ALL AVAILABLE DATA

Further analyses have been carried out combining the first and second family samples, totalling 149 families with 301 children, 156 males and 145 females.

The distribution of total ridge-count in parents and children of these families is given in Table 5. As each child has been entered with each parent, there are 602 parent-child pairs. The value obtained for the parent-child correlation is 0.50, the interparental correlation being 0.05 _+ 0.08. Mother-child and father-child correlation tables are shown respectively in Tables 6 and 7. The correlations between m0the.m and children and between fathers and children are alike, r = 0.49 ? 0.04 for the former, and r = 0.50 k 0.04 for the latter.

Table 5. Distribution of toW rtdqe-ccrunt in parents and children of 149 familiecl (with sex correction)

Ridge- count of parent

280-299 Z b 7 9 240-259

200-219 220-239

180-199 160-179 140-159 120-139 locr119 80-99 60-79

Ridge-count of child

s6 i Io2

260-279 Tota

I

5

17 49 81 95

92 59 40 60

8 6

I 2

56

21

602

In calculating correlations between one parent and children of one sex the appropriate data from 13 incomplete families (ie. where no prints available for one parent) have been used in addition to those from the combined sample. For estimating the mother-son correlation (see Table 8) the ridge-counts of I85 p a h were available, 156 from the complete families and 9 from

Page 6: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

SARAH B. HOLT

WP WuDt of mother

w - 56oyp- -59 2-39 wc-219 1 b 1 9 9 160-179 14-159 lscrI39 100-119 h - -9 40-59 3639 019

Total

276

0-19 -39 -- - - - - - -

- - - - - - - 2 I I - I

3 3 2 - 2 - I - -

~ - - 4 12

Table 6. Mother-child correlation table. Data from 149 familiee (with sex correction)

Ridge- count of mother

2a0-299 260-179

2-239 -259

200-219 180-199 160-179

120-139 '40-159

100-119 8 0 - 9 9 - 4-59 20-39 -19

Total

Tots

0-19 20-39 40-59 ~ - - - - - - - - - - - - - - - - - - - - - - - - - 2 - I - I - - -

1 -

6 - 7 9 1 1 - - 1 - - - - - - -

~ - - - 2 5 I

40-59 -259 -19 a-239

I 0 9 7 31 47 35 34 45 24 23 29 a 4 4

301

-

- 2 I 2

5 4 I I I -

3

5 5 3

-

I I 4 - I -

I

30 I-

23

Table 7. Father-ehild correlation table. Data from 149 familie8 (with 8ex correction)

- I -

10 : I - 1 - 1 -

23 17 3 1 1 30

Table 8. Mother-eon correlation table. Data from sample of 149 fam&%, and f r m 9 familiea where no prinh available for father (with sex correction)

60-79 100-119 220-239 240-259

- 2 I I 2

1 - I -

6 - 17

Page 7: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

276 GENETICS O F DERMAL RIDGES the incomplete. The value of r is 0.41 f 0.06. There were data for 166 pairs for constructing the mother-daughter correlation-table (Table 9), i.e. for 10 p a h in addition to the 146 from the family ample. The value of the correlation coefficient is 0.60 f 0.05. The mother-daughter correlation (0.67 f 0.08) waa the only one of mven parent-child correlations to be a@cantly different from 0.5 in the first 50 familiea. The value for the new ecrmple alone is r= 0.63 f 0.07. The incomplete familiea yielded data for three father-son pairs but none for father-daughter pairs. The distribution of total ridge-count for fathers and sons (169 pairs) is given in Table 10 and for fathers and daughters (146 paira) in Table 1 1. The estimate of the father-eon comhtion im 0.65 k 0.06; that of the father-daughter correlation 0.46 f 0.07.

Table 9. Motherdaughter melation table. Data from ample of 149 families, a d from 8 f a m i l k where no prhla available for father (with 8ex Correctbn)

count of - mother 0-19

-19 - 16o-Itp - 140-159 -

40-59 I -

I Ridgbcount of daughter

1-1 I9 aoo-219

- - a

3 4 4 5 5 a 3

I

-

29 18 '5

- I - 3 6 a I -

-39

I I

I= obf 0 0 5 .

Table 10. Father-son melation table. Data from sample of 149 families, and from 2 families where tu) pi& available for &her (actual counts)

Page 8: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

SARAH B. HOLT 277

The seven types of parent-child correlation and the interparental correlation for the 149 families are compared with the correeponding correlationa previously eathated from 60 families in Table 12. The z teet (Fisher & Yates, 1938) has been used for testing whether any of these parent-child correlations is eipficantly Merent from 0.6. In no case is the difference in z values greater than twice the standard error ( l / , / ( n - 3), where n is the number of pairs in the sample), although the Werence in respect to mother-daughter correlation is approaching this value.

First sample Second eample

(Actual counts) (Using sex correction) 50 families I 0 0 familiea

Table 11. Father-daughter Correlation table. Data from mmple of 149 familiw (with 8ex Correction)

Samplea combined

(Ueing sex correction) I49 f d W *

Ridge count of father

Ridge-count of daughter

- I - - - I

3

4 I

2 2 I -

I

3

5 4 8 3

2

I - I -

a I I

4 - I -

- I - I -

-

Total 3 I4 28 11 I 0 a

Correlation I E;f 1 orr relation NO. of Correlation NO. of coefficient coefficient I pairs I coefficient 1 - 1

Parent-child Mother-child Father-child Mother-son Mother-daughter Father-son Father-daughter

212 I 0 6 I 0 6 5 3 5 3 5 3 5 3 -

0'02 f 0' I 0 1 0 0 0.05 f 0.08 I 4 9 Parent-parent 50

* Twins omitted from first sample and 4 extra children included. (See text). t Data included from 9 f d e e where no prints available for father (9 pairs). $ Data included from 8 f d e a where no pMta available for father (10 pairs). f Data included from 2 f d e a where no prints available for mother (3 pairs).

Page 9: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

278

6 / 2 1 : 26 I 33

G E N E T I C S O F DERMAL RIDGES

21

MIDPARENT-CHILD CORRELATION AND REGRESSION

For estimating midparent-child correlation the sons and daughters have been considered separately, the actual ridge-counts being used. The midparent-son correlation table for the combined samples is given in Table 13 and the midparent-daughter in Table 14. The midparent- aon correlation coefficient, calculated from 156 pairs, is 0.64 0.05, which by the z teat is not significantly different from the theoretical value of 0.7 1. The midparent-daughter correlation is 0.71 & 0.04, the number of pairs being 145.

Table 13. Midprent -8on curr&ion fable (actual counts)

Table 14. Midparent-duughter correlation table (actual cozcnta)

Total ; o ( 0 1 4

160-1795

- - I I

3 4 4 3 2 I -

I

20

The midparent-child correlation and regression coefficients are shown in Table 15. The midparent-child correlation, 0-67 f 0.03, was found by combining the data in Tables 13 and 14, arid again no sex correction w'm made. The regression coefficient for son on midparent is

Page 10: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

SARAH B. H O L T 279

0.806, while that for daughter on midparent is 1.002. These values are not significantly different from one another by the standard method for calcubting the standard errors of regressions.

In order to test for recessivity by Penrose’s method, values of F(z), the observed average child ridge-count for a given midparent value 2, were plotted against values of 2. This was done separately for sons and daughters. The regression of total ridge-count of sons on midparent value is shown in Fig. 1 and for daughters in Fig. 2. In both diagrams the fitted linear regression line is given. There is no apparent deviation from linearity in either case, and hence no sign of dominance.

Table 15. Hidparent-child correlations f m total ridge-count (149 families)

Midparent-child Midparent -Eon Midparent -daughter

Correlation 1 No.of Regression coefficient coefficient pairs (child on midparent)

0.67 f 003 301 0.91 I 0.64 f 0.05 156 0.805 071 f 0.04 I45 1’002

CONCLUSIONS The results confirm the earlier ones. Allowing for any inadequacies of the methods used, the parent-child correlation for total ridge-count cannot be very different from 0-5. This leaves little room for any dominance effect, since dominance reduces the parent-child correlation and to a much greater extent than it does the sib-sib correlation (Fisher, 1918). The evidence from midparent-child correlation and regression also points to dominance being absent and to the alleles concerned being additive. Nor is there any suggestion of an appreciable environmental effect (the values of mother-child and father-child correlations being similar). Such an effect would of necessity be maternal, for only conditions in utero can affect the formation and aline- ment of the dermal ridges. Presumably, the environment has effect over a short period only, aa the ridges are completely formed by the end of the fourth foetal month. With the time factor limited in this way, it is hardly surprising that the environmental effect is apparently small.

Recently Pons (1954) has reported similar results for the transverseness of palmar main lines. Using Cummins’s index he obtained parent-child, mother-child and father-child correlations not significantly Werent from 0.5. Moreover, the value of the midparent-child correlation was 0.72 f 0.05, while the regression of offspring on midparent value was linear.

SUMMARY Parent-child correlations have been estimated for total ridge-count using new data from 100 families with 104 sons and 91 daughters.

Parent-child, mother-child and father-child correlations are not significantly different from 0.5. The interparental correlation is 0.02 f 0.10.

The new data have been combined with the earlier data. from 49 families. The parent-child correlation estimated from this total sample is 0.50, the mother-child correlation 0.49 4 0.04 and the father-child 0.50 k 0.04. Mother-son, mother-daughter, father-son and father-daughter correlations are not significantly different from 0.6.

Page 11: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

2 80 GENETICS OF DERMAL RIDGES

I I I I I I I I I 30 50 70 90 110 130 150 170 190 210

Fig. 1. Regremion of total ridge-count of mne on midperent value. Obeerved mesne and fitted etraight line are shown. P(x) is the obeerved average son vdue for a given midparent value, 2.

210 r

190 -

170 -

150 -

130 - 110

Y ( 4 - 90-

70 -

5 0 -

30 30 50 70 90 110 130 150 170 190 210

2

Fig. 2. Regxtdon of total ridge-oount of daughters on midparent value. Observed means and fitted straight line are shown. p(z) is the obeerved average daughter value for a given midparent value, 2.

Page 12: GENETICS OF DERMAL RIDGES: PARENT-CHILD CORRELATIONS FOR TOTAL FINGER RIDGE-COUNT

SARAH B. HOLT 281

Midparent-child correlation coeffioienta agree with the theoretical value I/ J2 (midparent-son, r = 0-64 f 0-06; midparent-daughter, r = 0.71 f 0.04). The regreasions for total ridge-count of both sons and daughters on midparent value am linear.

These results confirm earlier ones. There is no indication of dominance, nor is there evidence of a maternal (environmental) effeot.

REFERENCES

FISEEB, R. A. (1918). The correlation between relativee on the suppwition of Mendelian inheritance. Tram.

FISHEB, R. A. & Yams, F. (1938). Stotbticd Tablee for Bwlogicd, A g r k u h d and Medakd Reaccrtch,

Glatm~, F. (1889). Na#und I- . London: Maormllen * and&. HOLT, S. B. (1962). Genetics of dermal ridgee: inheritance of total &Iger ridge-oount. Ann. Eugen., Lond.,

17, 140-61. HOLT, 8. B. (1966). Genetice of dermal ridgee: frequency diatributione of total f h p r ridge-count. Ann.

HOLT, 9. B. (1966). Proc. 9th Int. Congr. ffazel. Pt. 11. Ceryologia, suppl. (Abstr.) (in the Preee). PENROSE, L. S. (1949). Tha Bidogy of Mentd &feet. London: Sidgwick and Jackeon Ltd. PONS, J. (1964). Herencia de 1- lineee principdee de la pelme. Contribucih a le gen&iccr de lm caracteres

Roy. Soo. Edinb. 52, 39Q433.

let ed. Edinburgh: Oliver and Boyd.

Hum. ffmt., Lad., 20, 168.

dermoppilaree. Tmb. Inat. S-n Antrqp. 14,36-60.