188 KANSAS UNIVERSITY SCIENCE BULLETIN. 



element as described for Xiphidium, which passes into the first 

 spermatocyte as a formed chromosome, while its fellows break 

 up into the spireme. 



In the anaphase the chromosomes are drawn away from the 

 equator, and extend lengthwise of the spindle as long rods. 

 During the telophase the disintegration of the chromosomes 

 takes place rapidly, and, for a time, the individual chromosomes 

 may be distinguished in the loose masses of chromomeres. 

 This distinction, however, is soon lost, and the nuclear vesicle 

 becomes covered with fine and apparently unrelated chromo- 

 meres. It is at this point that the transformation of the cells 

 from second spermatogonia to first spermatocytes takes place. 

 So long as the chromosomes are present in the somatic number, 

 we have to deal with spermatogonia, but when the disintegrat- 

 ing process comes upon them and they are lost to view as 

 distinct entities, then is reached the end of destructive sper- 

 matogonia! changes, and upon their reconstruction they are 

 chromosomes of the spermatocytes. 



(c) The First Spermatocytes. 



The main features characterizing the next steps in the proc- 

 ess are the rapid increase in size of the cell and nucleus, and 

 the arrangement of the chromomeres into a fine thread or 

 threads (figs. 2-4). This is well called the growth stage, for 

 all parts of the cell engage in the work of regaining the ground 

 lost during the period of multiplication in the secondary sper- 

 matogonia. As a result of this metabolic activity, the first 

 spermatocytes at the end of the prophase have reached a vol- 

 ume often as much as ten times that possessed by the last gen- 

 eration of the secondary spermatogonia from which they were 

 derived. Nucleus and cytoplasm, in about an equal degree, 

 participate in this enlargement, and, at the end of the period, 

 present an appearance much different from that of the sper- 

 matogonia. This consists most strikingly in the greater clear- 

 ness of all the parts, due to the increased amount of hyaloplasm 

 which separates by greater distances the more solid structures 

 of the cell. 



In the nucleus, for insance, the chromatin aggregates are 

 now definitely apparent, and each stands free and clear except 

 for connecting threads of linin. The cytoplasm, likewise, in- 

 stead of showing a coarsely granular aspect, exhibits a clearly 



