428 



Mr. G. Smith. 



of growth on the other ; triat the parthenogenetic females which are kept 

 crowded at low temperatures tend to store fat in place of glycogen and to be 

 retarded in growth ; that this tendency reaches its maximum in the sexual 

 forms ; and that these sexual forms are produced only by the crowded 

 parthenogenetic females which have a tendency to store fat and to be 

 retarded in growth. The conclusion to be drawn from this series of facts is 

 that the induced fat-storage and retarded growth of the parthenogenetic 

 females crowded at low temperatures are the causal forerunners of the 

 production of the sexual forms. 



If we regard the parthenogenetic mode of reproduction as being essentially 



Fig. 8.- — Adult, fortnight old, male, showing reserve material present in the form of fat. 



a form of discontinuous growth or budding, we may observe that this is 

 favoured by the conditions which also induce rapid growth in general, 

 namely, preponderant storage of glycogen under the conditions of isolation 

 and high temperature. The production of the sexual forms, which grow 

 slowly and reproduce with extreme tardiness, is accompanied by a pre- 

 ponderant storage of fat, under the conditions of crowding and low 

 temperature. 



It is claimed, therefore, that the manner in which external conditions 

 determine the continuance of parthenogenesis or the production of sexual 

 forms is as follows : The condition of isolation and high temperature favours 

 the storage of glycogen as opposed to fat, and this storage of glycogen leads 



