Manchester Memoirs, Vol. I. ( 1 906), No. 6. 2 1 



Tiere zutrefifend sein kann. Die eigentiimlichen Fort- 

 pflanzLingsverhaltnisse der Honigbiene, der Gallwespen, 

 der Daphniden, der Rotatorien, des Dinophilus, u.s.w. 

 lassen sich nicht in dieser Weise aufklaren,' is of itself a 

 sufficient reason for not accepting it, were it not otherwise 

 unsatisfactory, as Morgan (71) has shown. 



It is not by excepting these 'pecuh'ar' cases of 

 parthenogenesis, but by studying them, that we shall 

 have more light thrown upon the problem of sex. The 

 solution of the problem of the determination of sex is still 

 far off, and will continue so until we have more evidence 

 than is available at the present time. 



The view that nutrition is an important factor in the 

 determination of sex has received some support. Siebold 

 (84) first showed that in the saw-fly {Nematus ventricosus) 

 more females than males were produced when abundant 

 nutrition was available. Maupas (61) was able to control 

 the sexes of Hydatina by feeding. Other evidence is 

 afforded by Nussbaum on Hydatina. Hoffmann (52) from 

 his study of plants came to the conclusion that the males 

 were incompletely developed individuals, formed under 

 unfavourable conditions. The Lepidoptera have furnished 

 material for many experiments with a view to finding out 

 the effect of nutrition on sex. Mrs. Treat (lOO) stated that 

 males and females were formed according as the 

 caterpillars were poorly or well-fed, Cuenot (22), however, 

 was unable to come to this conclusion from his experi- 

 ments, and Kellog and Bell (53) experimenting on the 

 same insects failed to obtain evidence in support of it. 

 The difficulties in investigating the effect of food on 

 caterpillars are considerable, the chief being that the 

 female imagines are larger than the males, and con- 

 sequently require more food during their larval stage, any 

 diminution then in the quantity of the food will affect the 



