BBCKNT RESEARCHES ON SPERMATOGENESIS. 335 



myself in Helix by division of the nucleus. He accounts for 

 the discrepancy in the observations by supposing that the former 

 observer obtained deceptive appearances byatoo prolonged action 

 of osmic acid. The object with which his observations were 

 made was to assign some explanation to the striking fact of the 

 presence of two kinds of spermatozoa — the hair-like form and the 

 worm- like form — in Paludina. He found that only the small 

 hair-like form was concerned in the fertilisation of the ovum, in 

 which process the other larger form took no part, and, as far as 

 he was able to determine, this latter had no function at all. 

 Having failed to find any physiological reason for the presence 

 of this form, he was obliged to fall back on morphological 

 explanations, and the hypothesis he oflFers is that this large 

 form represents a disturbed or arrested development of a sper- 

 matozoon ; that the cell from which it arises is, as it were, a 

 female cell, and that the testis, as seen in Paludina, is a transi- 

 tion form to the hermaphrodite glands of Pulmonates and 

 Opisthobranchs, in which the distinction between male and 

 female cells is at an early stage impossible. 



