No. 598] SHORTER ARTICLES AND DISCUSSION 



629 



made 11 in a memoir dealing with plant materials and eertain 

 special problems more minutely analyzed on further sets of 

 data. 12 



In the mammal, the relationship between fertility and so- 

 matic characters may be determined from (a) the somatic char- 

 acters of an individual mother and her fertility, or (6) the 

 characteristics of the progeny which serves as the measure of the 

 fertility of a mother. Obviously, these two methods of operation 

 are biologically not at all comparable. 



The economic importance of the possible correlation between 

 bodily characteristics and fertility has naturally given rise to 

 many popular beliefs concerning the existence of such a relation- 

 ship. Wentworth and Aubel 13 have, however, found no evidence 

 of such in a comparison of the mean litter size in "large type" 

 and "small type" hogs. 



Pearson has shown 14 from Captain Lloyd's data 15 that there is 

 a sensible and almost linear relationship between weight of 

 mother and number of young in litter in Poona and Belgaum 

 rats. The intensity of the correlation is, however, low, of the 

 order r = .160. 



Data for the full interpretation of such relationships are much 

 needed but not as yet available. The problem is evidently one of 

 great complexity. As Pearson points out, at eertain stages of 

 pregnancy the number of young might actually influence, by its 

 own contribution, maternal body weight. 16 Furthermore, in 

 these rodents growth continues notwithstanding pregnancy, and 

 one might expect some correlation between weight of mother and 

 size of litter as a resultant of the relationship between the age of 

 the mother and her own weight and the age of the mother and 

 the size of her litter. 



Minot found that the over-gain in weight of pregnant guinea 

 pigs is not all lost after delivery 17 and Watson 18 many years ago 



11 Karris, J. Arthur, Biometrika, 8: 52-65, 1910. 



is Wentworth, E. N. and C. E. Aubel, Jour. Agr. Bes., 5: 1148, 1916. 

 ^"Pearson, K., "Darwinism, Biometry and Some Recent Biology," I, 



15 Lloyd, R. E., "The Relation between Fertility and Normality in Rats," 

 Bee. Ind. Mus., 3: 261-265. 



i« Minot (Journ. Phys., 12: 141-145, 1891) has shown that in the guinea 

 pig there is a relatively enormous over-gain in weight before delivery. 



" Crampe (loc. cit.) has given certain data on the weight of mothers after 



™ Watson, J. B., < ' The Effect of the Bearing of Young upon the Body 



