STUDIES ON CHROMOSOMES 395 



cal spirit. It was only after prolonged and repeated study of the 

 same objects, in part of the same preparations, as those of the 

 Schreiners and of Janssens, that this scepticism gave way to the 

 belief that the conclusions of these observers (not to mention 

 others) are probably well founded. I will not at this time pub- 

 lish new figures or photographs of these forms (of which I have a 

 large number, particularly of Batracoseps) but will here confine 

 myself to a brief statement of the main reasons why I do not find 

 it possible to accept the adverse criticisms that have been indi- 

 cated. 



There are two points that demand especial emphasis. One is 

 the complete demonstration of the seriation of the stages that is 

 afforded in the testis of Batracoseps. The regular and panoramic 

 progression of stages from the spermatogonial end of the testis 

 to that of the spermatids renders error on this point out of the 

 question; and in particular, there is no possibility of confusing 

 the post-synaptic with the pre-synaptic stages, or the synaptic 

 nuclei with those of the early prophases (pro-strepsinema) of the 

 spermatocyte-divisions. The second point of importance is the 

 essential accuracy of the figures of the Schreiners and of Janssens 

 indeed, my only criticism of those of Janssens might be that the 

 relations are often shown even more clearly in the preparations 

 than in his figures, perhaps because the latter were in some cases 

 made from material not quite as perfectly fixed as the best that has 

 come under my observation. In the case of Tomopteris I have 

 been able in a considerable number of cases to compare the figures 

 of the Schreiners with the identical nuclei from which they were 

 drawn. Here and there, perhaps, certain details might be some- 

 what differently represented by different observers; but a study 

 of very numerous cells at every stage of the spermatogenesis has 

 thoroughly convinced me that as a whole the figures of these 

 authors present a faithful picture of what any observer may see 

 in the preparations. The only question that can be raised seems 

 to me therefore to be a matter of interpretation. 



I think that any observer, whatever be his individual preposses- 

 sion, who will take the trouble to study these preparations thor- 

 oughly, will find himself compelled to admit the following facts: 



