RELATING TO SECONDARY SEXUAL CHARACTERS. 91 



of a spermatogonial cell, of such a kind that both sex chromosomes 

 (in the case of insects at least) got into the same cell might be expected 

 to cause such a cell to become, even in the male, an egg-cell rather 

 than a sperm-cell. The degenerative changes of the testes in the 

 hermit crab caused by the parasite might be imagined to favor such 

 abnormal division with its consequences. More significant, however, 

 is the fact that the parasite causes the absorption of the ovary when 

 it infects a young female, so that even all its eggs disappear. In other 

 words, the parasite is as injurious to the peculiarly female organ as it 

 is to the testis. Why, then, one can not but ask, should an influence 

 that causes such effects on the ovary first change a male into a female 

 so long as it is present and then when the parasite has disappeared leave 

 an influence behind of a kind that causes the ovary to develop — ^an 

 organ which the parasite destroys when the parasite is present? Is 

 it not more probable that only the secondary sexual organs were 

 changed, without change in sex, the single case of eggs observed being 

 caused in another way? This point can only be settled by direct exper- 

 imentation either by removal of the testis, by injuring it, or by injection, 

 grafting, or feeding experiments. The extent of the testis and its position 

 make it impossible to remove it by an operation, as I have found after 

 repeated attempts. It seemed easier to destroy it by radium. This I 

 have tried to do, using very powerful tubes, treating the crab (fiddler 

 crabs) for several hours. The crabs had had one claw removed — the 

 enormously large one — ^and were kept until the next molt, that occurred 

 from a week to six weeks later. In none of the cases was any change 

 produced. The large claw of the male regenerated, of course, not full 

 size after only one molt, but after several nearly full size and always 

 with the peculiarities of the male crab. The abdomen and the appen- 

 dages were not changed. Whether the significant cells of the testes, 

 if there are such cells apart from the germ-cells, were destroyed, can 

 not be told, for as yet the histological examination of the material has 

 not been made. Until a successful operation has been done, I think 

 we must hesitate to accept Smith's argiunent, although based as it is 

 on a series of interesting observations. His speculation is as follows: 



"The reason why Sacculina causes the assiimption of the adult female state 

 in Inachus is found in the facts: (1) that the roots of Sacculina elaborate a 

 yolk-substance from the blood of Inachus of a similar nature to that which is 

 elaborated in the ovaries of an adult Inachus; (2) that in order to elaborate this 

 yolk-substance the roots take up from the blood of Inachus the female sexual 

 formation substance, which is the necessary material for forming the yolk; (3) 

 that the female sexual formative substance being absorbed by the Sacculina 

 roots is regenerated in excess; (4) that the presence of the female formative 

 substance continually circulating in large quantities in the body-fluids of the 

 infected crabs causes the production of adult female secondary sexual charac- 

 ters, and, when the parasite dies, of yolk-containing eggs." 



In brief, the evidence consists in showing that in the parasite a yolk- 

 substance appears, which Smith says comes from the blood of the crab 



