210 



doubt, and efforts to prove that only one is in operation are 

 not likely to meet with much success. Investigations into the 

 physico-chemical nature of organism promises to reveal inter- 

 esting results. Cell association is another subject of great in- 

 terest, whether we are considering ontogeny or phylogeny. In 

 this connection jDolyemhryony is instructive, for here we see 

 a group of cells which left in association will form one organ- 

 ism, each cell forming a certain part, but if these cells be sepa- 

 rated each one becomes a complete organism. Kegeneration 

 appears to be similar to polyembryonism. Another instructive 

 case is the absence or presence of certain cells, such as the 

 testes, in an organism. Every biologist should be familiar 

 with the many cases of this nature on record. A recent ease 

 is that of Dorothy of Orono,* the Ayrshire cow ; this animal 

 assumed characters of the male, both in structure and be- 

 havior, and the only abnormality that could be observed was 

 a slight difference in the follicles so that no corpora lutea 

 were formed. 



When collecting at Kilauea in January, I was surprised 

 to find a number of male specimens of Delphacids in Avhich 

 the external genital organs were abortive or improperly de- 

 veloped. In all such cases I found that the testes had been 

 destroyed by parasites, either by Pipimculu,s or StyJopids; 

 when parasites were present but no damage done to the testes 

 there was no malformation of the external genitalia. The 

 chief alterations were in the reduction of the aedeagus^ the 

 reduction or absence of the anal spines, the reduction of the 

 genital styles and of the mechanism that coordinates the move- 

 ments of the anal segment, aedeagus and genital styles. If 

 the destruction of these cells can bring about such a distinct 

 alteration as this it shows that th^re is a very intimate asso- 

 ciation between them and the exiernal genitalia, and that the 

 development of the latter depends upon the nature of the for- 

 nu'i-. Is it not possible that a change in the nature of these 

 c*.'lls, either chemically or physically or both, may bring about 

 a change in the form of the genitalia, and that the aedeagus 

 is the most susceptible of the genital organs to such changes ? 

 We might even speculate further and consider a correspond- 



*Pearl and Surface, Science 1915, No. 1060, p. 616. 



