STUDIES IN THE. EXPERIMENTAL ANALYSIS OF SEX. 237 



blood of luaclius the female sexual formative substance, 

 which is the necessary material for forming the yolk ; (3) that 

 the female sexual formative substance, being anchored by the 

 Sacculinaroots,is regenerated in excess; (4) that thepreseuce 

 of the female sexual formative substance continually circulat- 

 ing in large quantities in the body-fluids of the infected crabs 

 causes the production of adult female secondary sexual 

 characters, and, when the parasite dies, of yolk-containing eo-fs. 



4. On a Case of Paiiasitic Castration in a Vertebrate. 

 Although numerous cases are now known of the presence 

 of a parasite causing arrest of development or degeneration 

 of the reproductive organs in various invertebrates, no clear 

 instance of this process has been reported, so far as I am 

 aware, among vertebrate animals as the result of bacterial 

 disease of organs other than the reproductive organs them- 

 selves. Of course, where the reproductive organs themselves 

 are the seat of infection, a certain amount of atrophy or 

 degenei'atiou may naturally result, but we have here to deal 

 with a case of parasitic castration, analogous to the case of 

 Sacculina on Inachus, or of Entoniscus on various 

 crabs, where the reproductive organs are not themselves 

 necessarily attacked by the parasite, but are secondarily 

 affected by the general disturbance of the metabolism, set up 

 by the presence of a parasite in other parts of the body. 



During December, 1909, I received a pure-bred Gallus 

 bankiva cockerel for breeding purposes. It belonged to 

 the breed known as tiie Indian Jungle Fowl, a breed which 

 has departed very little from the wild Gallus bankiva. 

 The bird when it arrived appeared in good health; the 

 plumage was in good condition, the comb and wattles well 

 developed and red, the spurs fully developed, the tail carried 

 •erect, and the bird crowed in the noi-mal manner. Its age 

 was one year and a half. About two weeks after it arrived 

 it showed signs of sickness and a tendency to mope in the 

 straw at the back of its run. These symptoms became 

 gradually worse, and at the beginning of February the whole 



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