The Spermatogenesis in Peutatoma up to thie Formation of the Spermatid. 37 



albumen solution with which the sections were fastened to the slide, 

 since the latter fluid remains colorless. It may be noted that in the 

 two testicles of Peniatoma studied, as well as in the two of Tropi- 

 coris, the two follicles containing the larger generation of cells have 

 exactly the same position with regard to the other follicles, the one 

 being at the periphery of the testicle, the other separated from it by 

 a follicle containing cells of the small generation (Figs. 225, 227, 

 PI. 5) ; on this account the larger size of the cells in follicles 1 and 

 3 can in no way be regarded as an artefact. There appear to be 

 fewer cells in the follicles of the large generation, than in those 

 containing the small generation. The number of cells forming cell 

 syncytia in follicles 1 and 3 appears to be about the same as in the 

 other follicles ; at the first I expected to find a greater number, and 

 to explain the greater size of cells of the large generation by assuming 

 that in follicles 1 and 3 all the cells take part in the formation of 

 syncytia, but further study showed that this is not the case. 



Most of my figures and descriptions apply to cells of the small 

 generation, those of the larger (marked by an asterisk in the figures) 

 being introduced mainly for comparison. This is due to the fact of 

 the necessity of thin sections for study, sections which at the same 

 time must show the nuclei in their entirety, while only thick sections 

 show whole nuclei of cells of the large generation. And a further 

 reason is that the cells of the small generation are twice or thrice 

 as numerous as those of the large one (there being 4 follicles of the 

 small generation), and hence the various stages of cells of the 

 small generation are found more abundantly. But with the exception 

 of a few minor differences, which shall be mentioned, the two kinds 

 of spermatocytes undergo exactly the same changes. 



d) The rest stage. 



At this stage the spermatocytes attain their greatest size, though 

 a further swelling of the nucleus is found in the succeeding pro- 

 phases. The resting cells of the large generation have comparatively 

 enormous dimensions, nearly the size of corresponding cells in Sala- 

 mandra and Plethodoii, so that they are most beautiful objects for 

 investigation. Of course under the term "rest" is understood "rest 

 from division" alone , since at this period the metabolic activity of 

 the cell is probably at its height. 



The rest stage (Figs. 95—100) is not sharply demarcated from 

 the end of the telophase nor from the beginning of the prophase; its 



