292 KANSAS UNIVERSITY SCIENCE BULLETIN. 



ZOOLOGICAL LABORATORY. 



conjugated he should have given some intermediate stages 

 showing the two moving together. In some cases (his fig. 20) 

 the N structure is almost as large as his bivalent heterochro- 

 mosome, which leads us to suspect that probably his nucleolus 

 was in reality what he mistook, part of the time, for one of 

 his heterochromosomes, and that his heterochromosome is not 

 a bivalent structure. In speaking of the bivalence of the 

 latter, at this point, it might be asked why his heterochromo- 

 some in the vesicle stage of the prophase of the last sperma- 

 togonia! division should at first be a single element, then seg- 

 ment and remain separate during the metaphase as two hetero- 

 chromosomes, and then in the first part of the rest period 

 thereafter between the spermatogonium and the spermatocyte 

 should conjugate again. This, too, seems unreasonable and 

 improbable. From here on, throughout the remainder of the 

 growth period, he finds but two bodies present, the "bivalent 

 heterochromosome" and the "irregular nucleolus." 



My work upon Syrbula admirabilis gives rise to two views 

 regarding his N2 structures in his figure 13. The first is that 

 one of the bodies is the accessory seen in end view and the 

 other body, of course, the true nucleolus. But if these struc- 

 tures are exactly the same size, as is quite likely the case, a 

 second and more probable explanation is that he has not seen 

 the accessory at all in this cell but has shown the two nucleoli 

 which we find so often present in admirahilis in the early part 

 of the growth period after the last spermatogonia! division, 

 as shown in figure 10 of this paper. What adds support to 

 the latter view is the presence of two similar bodies in his 

 figure 1 of a resting spermatogonium. What we have seen 

 in admirahilis (fig. 7) convinces me that these two nucleoli 

 in the spermatogonium are not heterochromosomes, for that 

 element may always be found in the reticular condition in a 

 vesicle of its own applied close against the nuclear wall. That 

 there were two of these nucleolar bodies very generally pres- 

 ent in acuticornis is confirmed by Montgomery in his own 

 words : "With great regularity there is found in each nucleus 

 two or three larger, somewhat irregular, deep-staining bodies. 

 Whether they are nucleoli or heterochromosomes could not be 

 decided by the use of the iron-hsematoxylin stain." By using 

 Flemming's tricolor stain, and also by careful observation of 

 all prophase stages, I have decided that the bodies in question 



