76 KANSAS UNIVERSITY QUARTERLY. 



somes, and which, therefore, are the earliest to divide, are called the 

 "first spermatocytes." Those having diad chromosomes in the meta- 

 phase are denominated "second spermatocytes.'' By the division of 

 these the spermatids are formed. There is no resting condition of 

 the cells between the two divisions of the speripatocytes. 



When the two spermatocyte divisions are completed, the end of 

 cell division is reached, and the subsequent changes undergone by 

 the cells are merely transformations. These changes are experienced 

 by the spermatids, and, at the completion of their metamorphosis, 

 they become spermatozoa, the mature elements of the male sexual 

 organs. 



Regarding the stages of the division processes, I recognize four, 

 depending upon the condition of the chromatin. These are (1) the 

 prophase, during which the chromatin takes on the form of a thread 

 and then divides by cross-division into a number of segments called 

 chromosomes. This stage terminates and (2) the metaphase begins 

 when the chromosomes become arranged in the equatorial plate. The 

 metaphase witnesses but a single change in the chromatin, the sepa- 

 ration of the halves of the chromosomes. As soon as this is com- 

 pleted and the daughter groups of chromosomes commence their 

 movement towards the two poles it is ended, and the succeeding stage, 

 (3) the anaphase, is inaugurated. This comprises all the movements 

 of the chromosomes from their position in the equatorial plate until 

 they are grouped at the two poles of the spindle; here it ends, and 

 the final stage, (4) the telophase, commences. These terminal 

 changes, included under the telophase, consist usually in a loss of 

 the identity of the chromosomes, the arrangement of the resulting 

 chromatin in a nuclear vesicle such as is characteristic of the resting 

 cell, and the separation of the halves of the mother cell by the growth 

 of a cell wall. This cycle of changes terminates and the next one 

 commences when the chromatin of the daughter cells leaves the dif- 

 fuse condition and inaugurates the formation of a spireme. 



In the spermatocytes, of course, there is no resting condition be- 

 tween the divisions, and therefore no reconstruction of the nuclei, so 

 that the termination of one cycle and the commencement of another 

 is marked, principally, by the growth of a cell wall between the di- 

 asters. Applying this method of designating stages in the process of 

 cell division to the cells of the, insect testis, we would mark the end of 

 the spermatogonial divisions by the changes which result in the re- 

 construction of the nuclei and the formation of cell walls between the 

 last cells that divide with the somatic number of chromosomes in the 

 mitoses. The prophases which succeed this division belong to the 

 spermatocytes and have nothing further to do with the spermatogonia. 

 I am thus explicit in stating my position on this point because Mont- 



