vn] ABNORMAL SPERMATOZOA 103 



Finally, it should be mentioned that GOLDSCHMIDT (1915) 

 has shown, by growing spermatocytes and spermatids of 

 Moths in artificial cultures outside the body, that the 

 development of the spermatozoon is dependent on the 

 osmotic relations of the cells as controlled by the follicle 

 membrane in which the sperm-cells are enclosed. And he 

 makes the interesting suggestion, supported by some ex- 

 perimental evidence, that the abnormal spermatozoa, con- 

 stantly found in a number of Moths and Prosobranch 

 Molluscs, are produced by failure of the follicle membrane 

 to provide the necessary conditions for proper development. 

 In these species certain follicles become abnormal at an 

 early stage of the spermatocytes, and all the cells in the 

 follicles develop abnormally. In the molluscs some of the 

 nuclear matter, and in the moths all of it, is extruded giving 

 rise to so-called oligopyrene and apyrene spermatozoa, which 

 are apparently functionless 1 (cf. PI. X). They develop chiefly 

 in rather old testes, and in Moths, as GOLDSCHMIDT has 

 shown, are especially abundant in hybrids in which the male 

 characters are largely reduced. The explanation that they 

 are due to abnormal conditions consequent upon the failure 

 of the follicle membrane to supply the necessary conditions 

 seems more probable than any of the numerous other 

 speculations that have been advanced. 



Before passing on to consider the development of the 

 ovarian egg, a short space may be devoted to some accessory 

 structures in spermatogenesis found in a number of animals. 

 Frequently not all the primitive germ-cells give rise to 

 spermatozoa; some of them are used up in producing 

 accessory cells of various sorts. In mammals, for example, 

 among the spermatogonia which line the seminiferous tu- 

 bules of the testis, there are placed at intervals Sertoli cells 



1 Cf. MEVES (1903), KUSCHAKEWITSCH (1913), GATENBY (19170). 



