356 KANSAS UNIVERSITY SCIENCE BULLETIN. 



visible. (Figs. 26 and 28.) At this stage pairing of equal 

 elements is very common throughout the spermatogonial gen- 

 erations. Note the marked pairs in figures 1, 2 and 4, plate 

 LXV. It would seem from this that throughout the history of 

 the spermatogonial cells there is a consistent provision for the 

 final processes which mark the transition from spermatogonia 

 to spermatocyte. This process is called synapsis. The cells of 

 a mature spermatogonial cyst have not been counted, but judg- 

 ing from the number of cells in a cyst of developing sperma- 

 tids, eight mitoses complete the activity of the germ cells as 

 spermatogonia, that is, that after the last division there are 

 256 cells in a cyst. In such cysts the cells are poor in cyto- 

 plasm. 



After the final division the typical telophase is replaced by 

 synizesis. During this process the chromatin is contracted 

 into a deeply staining granular mass whose position within 

 the nucleus is either central or slightly eccentric, leaving the 

 peripheral area clear. It is quite certain that the chromatin 

 mass is composed of intimately associated granular threads, 

 for occasionally ends protrude from the knot, although entire 

 threads can not be traced. (Figs. 30, 33.) It is true that the 

 chromatin enters synizesis in the form of individual threads, 

 and the presynizetic stage is characterized by the same ele- 

 ments. It is reasonable to suppose that the threads continue 

 as such during the period of synizesis. That some change is 

 taking place within the knot is shown later, but there is no 

 evidence to show that this change involves the disorganization 

 of the chromatin threads and its reorganization into new ele- 

 ments. Nothing can be said in regard to the duration of 

 synizesis. That an end to end conjugation of the paired ele- 

 ments of the spermatogonial nucleus occurs during this period 

 seems established beyond a doubt. 



At one side of the conjugating threads lies a definite chro- 

 matin body of homogeneous consistency. Occasionally this 

 body shows an uneven outline suggesting a slight disintegra- 

 tion of the constituent chromatin. Its position is constant and 

 it is invariably present. From a study of subsequent matura- 

 tion processes it is shown to be the accessory chromosome 

 (McClung, Orthoptera) and can be identified as the homo- 

 logue of the unpaired element appearing in the spermatogonial 

 metaphases. In studying the history of this odd member of 

 the complex, drawings of it in that stage were made, as well as 



