378 THE GERM-PLASM 



In the case of bees, the factor that determines which of the 

 two halves of the ' female ' determinants is to become active, 

 seems to be the quality of the food supplied to the larva, 

 so that the critical moment only arrives long after the termina- 

 tion of embryogeny, and before the chrysalis stage is reached. 

 It is well known that when the queen is lost, another one is 

 produced by feeding a larval worker with royal diet. Thus the 

 sex depends on the occurrence or omission of fertilisation, but 

 the modification into a queen or worker takes place much later, 

 when the animal has reached the larval stage. The idea of the 

 trimorphism of certain determinants thus becomes much less 

 difficult to realise. We must look upon them as double-deter- 

 minants contained in the ids of the germ-plasm, the female 

 hemisphere of which is again composed of tw'o dissimilar 

 quarter-spheres. If the egg becomes fertilised the male half 

 becomes inactive, and we have already represented this figura- 

 tively as taking place by the ' female ' hemisphere extending 

 over the 'male' hemisphere, and enveloping it like a mantle. 

 This ' female ' ' determinant mantle ' consists of tw^o halves, 

 representing the queen and worker respectively, and we may 

 suppose that the subsequent determination during the larval 

 stage as to which half is to control the cell, takes place in such 

 a manner that the 'worker' half extends over the other when 

 the nourishment is poor, while with more abundant food the 

 * queen ' half grows more rapidly, and prevents the ' worker ' 

 half from exerting any influence on the cell. I naturally do not 

 in the least suppose that this figurative representation of the 

 process represents the actual facts of the case, but it at any rate 

 shows that the existence of trimorphic determinants — or more 

 accurately, of double-determinants each possessing a dimorphic 

 half — is conceivable. 



We might, however, also assume the existence of three in- 

 dependent determinants side by side, so arranged that they 

 become active under other definite influences ; and this con- 

 ception would better agree with the unavoidable assumption 

 that the three determinants which act vicariously are of a 

 similar size. 



The differentiation of the determinants into several equivalent 

 parts, each of which prevents the others from becoming active, 

 may take place to a still further degree by the ' ))iale ' half of the 

 doiible-deteniiiiuDits becoiuing differentiated into two dissimilar 



