74 KANSAS UNIVERSITY QUARTERLY. 



by the process of budding. A protuberance appears upon the nucleus, 

 is constricted ofiP, and, passing out into the cytoplasm, serves as a 

 center around which the food substance of the cell is formed. 



Thus, although the origin is similar in some respects to that I have 

 described for the itomere in the spermatids of Scolopendi'a, its later 

 behavior is very different. The itomere migrates through the cyto- 

 plasm, and is cast out through the cell-wall. The movement of this 

 structure through the cytoplasm is accompanied by the formation of 

 yolk material and the rapid growth of the cell, but its most important 

 function is quite different. In its migration toward the cell-wall it 

 seems to organize the cytoplasm and to mark out the course of the 

 future axial filament. 



The Origin of the Axial Filament. Regarding the origin of 

 the axial filament there seems to be much unanimity of opinion 

 among the more recent investigators. In 1895 Moore-*' found that, 

 in elasmobranchs, the axial filament is formed by the elongation of 

 the centrosome. Quite similar results were obtained by other inves- 

 tigators on the elasmobranchs, and in mammals and amphibians a 

 like origin is ascribed to this element. 



As regards its formation in arthropods, Paulmier-', in Anasa, speaks 

 of the axial filament as an outgrowth of the centrosome. Whether 

 by this he means that, beginning with the centrosome at the base of 

 the nucleus, the cytoplasmic reticulum is progressively condensed, or 

 whether he believes it to be formed by a mere elongation of the centro- 

 some, as in elasmobranchs, I cannot determine. 



In either case its origin does not correspond to that in Scolopendra. 

 In this material it certainly is not an elongation of the centrosome, 

 and, just as surely, is not a progressive condensation of the cytoplas- 

 mic reticulum, for at all stages all parts of the axial filament stain 

 exactly alike. In my observations I have attempted to exjjlain the 

 true origin of this structure, and it will not be necessary to repeat it 

 here. 



V. — SUMMARY. 



1. The spermatocytes, as they arise from the diffuse stage succeed- 

 ing the telophase of the last spermatogonial division, are small cells 

 with very little cytoplasm, the nucleus filling nearly the entire cell 

 body. The chromatin, with the exception of the accessory chromo- 

 some, becomes arranged in a spireme, and the proportional amount of 

 cytoplasm is much increased. 



2. The spireme breaks down, and a fine, weakly staining reticulum 

 is formed. This becomes finer and less prominent until it is no stronger 

 than the cytoplasmic reticulum. Meanwhile the accessory chromo- 



26. Moore, J. E. S., 1895, loc. cit. 



27. Paulmier, F. C. 1899, loc. cit. 



