25 



Bergen Museum to whose kindness and generosity I am deeply in- 

 debted. 



The questions at issue are essentially two. Dr. Nansen describes 

 and discusses the follicular epithelium of the testicular capsules, of 

 which I in my original paper made no mention. I shall not discuss this 

 point here further than to say that I think it extremely doubtful whether 

 the epithelium referred to is in any way comparable to the follicular 

 epithelium of an ovarian egg. I believe it to be most likely a germinal 

 epithelium homologous with that which lines testicular tubes in other 

 animals, and which in them gives rise to successive crops of spermato- 

 cytes. 



The second question is more important, and here the difference 

 between my original account and Dr. Nans en's admits of no ambi- 

 guity. Both of us have described and figured three principal cellular 

 elements seen in ripe or ripening capsules : 



(a) The spermatoblasts (Cunningham) or spermatides (Nansen), 

 large spherical or polygonal cells with a large nucleus, 



(b) spindle-shaped cells, bipolar, having a long attenuated process 

 at each end, 



(c) ripe spermatozoa. 



Dr. Nansen says that these are but three successive stages in the 

 formation of a single spermatozoon out of each spermatide. I stated 

 in my original paper that the spindle shaped cells were the part of the 

 spermatoblast left behind after two spermatozoa had separated from it, 

 each protoplasmic process of the spindle having been previously con- 

 tinuous with the tail of a spermatozoon. 



My original account of the spermatogenesis was certainly surpris- 

 ing to myself, and probably to those that read it. But Dr. Nansen 

 though he uncompromisingly contradicts my version of the process 

 gives no evidence of the correctness of his own. He says merely: »By 

 an elongation of the nucleus as well as the whole body of the cell, 

 these spermatides are now gradually transformed into ripe spermatozoa. 

 Fig. 1 1 caq represents part of a capsule containing spermatides and 

 spermatozoa, more or less developed. As to the details of the develop- 

 ment of the spermatides into spermatozoa, I will give no circumstantial 

 description here; my investigations of that branch of the subject are 

 not yet finished. From the little I have seen I think however that it is 

 evident that the spermatozoon is formed from the nucleus as well as 

 from the protoplasm of the spermatide, i. e. the whole spermatide is 

 transformed into a spermatozoon. As to the tail, that is perhaps formed 

 partly by an elongation of the nucleus partly by the protoplasm of the 

 spermatide«. 



