150 KANSAS UNIVERSITY QUARTERLY. 



membrane proper ; in some cases occupying a i^osition between the 

 "fingers" or sacculations of it (fig. 34). This vesicular stage is of 

 comparatively long duration, and is followed by a receding of the 

 cliomomeres from the membrane to form a chromatic rod, first loose, 

 rough, and granular, but gradually growing more slender and com- 

 pact, and often becoming twisted (fig. 16). It also betrays a longi- 

 tudinal split at a stage later than that at which a similar occurrence 

 is observable in the ordinary chromosomes. 



From the middle prophases to the telophases, its conduct is so simi- 

 lar to that of the other chromosomes that it would hardly be an error 

 to speak of the cells of these stages as having two nuclei, one having 

 a single chromosome and the other a large number, the small nucleus 

 always lagging slightly behind the large one. This lagging of the 

 accessory chromosome is nicely shown in fig. 21, already alluded to, 

 where in a stage just before the metaphase the nuclear membrane is 

 seen to be dissolved while that of the body in question is still intact. 



In the last or transformation division of the secondary sj^ermato- 

 gonia, some differences are noticeable in the behavior of the element 

 under consideration. The vesicular stage seems to be of slightly 

 longer duration, and while, after its close, the same condensation of 

 the chromatin takes place, no longitudinal split appears until the late 

 prophases or "ring stage" of the spermatocyte; and in the course of 

 the earlier prophases of the growth period its vesicle gradually be- 

 comes fused with the nuclear membrane, its outer half completing the 

 smooth contour of the latter, while its inner portion projects into the 

 nuclear cavity. In this stage it has the appearance of an irregular 

 vesicle filled with a homogeneous, darkly staining liquid or semi- 

 liquid body, suspended within the membrane of the nucleus. Later 

 it again becomes granular, and in the first spermatocyte division 

 divides as it did in the spermatogonia. 



The resting stage of this element, as shown by its staining violet 

 with Flemming's three-color stain, is what I have called the vesicular 

 stage, and this only, since at all other times it stains a bright red. 

 The absence of the formation of a .spireme at any stage in the de- 

 velopment of this element is paralleled by Henking's description of 

 the normal process in all the chromosomes in the sj)ermatogonia of 

 Pyrrhocor'hs. He says: "Wenn die jungen Hodenzellen sich 

 theilen woUen, so bekommt der Kern ein anderes Aussehen. Vorher 

 durchweg dunkel ( bei Behandlung-mit Flemming's Flilssigkeit ) wird 

 er nun licht, indem er sich aufblaht und zwischen die sich ebenfalls 

 nicht unerheblich vergrossernden Chromatinkorner eine helle Sub- 

 stanz einlagert. . . . Das Chromatin hat sich in getrennten, im 

 Allgemeinen ziemlich gleich weit von einander abstehenden etwa 

 kugeligen Kfirnern angehauft." 



