WILCOX: SPERMATOGENESIS. 7 



Figures 57-59 as two bodies, one of which is outside the nucleus, and 

 in Figures 50, 61, as two bodies, both outside the nucleus — seem to 

 rao to give evidence of being stages in the history of one and the same 

 body. My reason for thinking that they are genetically connected is 

 their similarity in size, structure, and reaction to stains. 



During the stages shown in Figures 49, 51, 52, there appears to be a 

 chemical change in the constitution of the chromosomes. By the 

 safranin and victoria-green method tlie chromosomes stain red, thougli 

 not so deeply as the nucleoli. At later stages the chromosomes assume 

 a green color, while the nucleoli continue to stain red. In still later 

 stages (as Figs. 50, 60, 61) the chromosomes again take the red. 



The metamorphosis of the spermatid could be worked out in consider- 

 able detail. The chromatin is first arranged around the periphery of 

 the nucleus (Plate I. Figs. 24, 27-30). The individual chromosomes 

 fuse into a thin shell of chromatin, surrounding, in part, the nuclear 

 space. This chromatic shell does not extend over the whole periphery 

 of the nucleus, and yet it is so extensive at the beginning of the meta- 

 morphosis that in certain views of the nucleus it has the appearance of 

 a complete sphere. 



Figures 15-18 and 24-45 show various stages in the spermatid meta- 

 morphosis. Figures 62-77 (Plate II.) present a series of the changes 

 which take place in the head of the spermatid. The stage in which the 

 chromatin (Figs. 66-72) has the form of a crescent is very common, and 

 therefore undoubtedly of considerable duration. 



The origin of the extranuclear body (Nebenkorper), w^hich is stained 

 dark green in Figures 20, 27-30, could not be determined. On the an- 

 terior end of the nearly mature spermatozoon (Fig. 1 c) is to be seen a 

 highly refractive curved tip. Just behind it is a small darkly stained 

 body. The body so conspicuous in the neck of the spermatid of Calop- 

 tenus (Plate V. Figs. 196-200) was very rarely seen in the Cicada, 

 probably because the methods used on Cicada would not stain it. 



Degenerating cells are very frequent in the testicular follicles of Cicada. 

 So far as my work on Cicada and Caloptenus goes, amitotic division and 

 degeneration affect only the spermatogonia, i. e. if the reproductive cell 

 reaches the spermatocyte stage, it completes its course. The first sign 

 by which I was able to recognize that a spermatogonium is becoming 

 abnormal is due to a chemical change in the nucleus. The chromosomes 

 stain more brightly than in normal cells. The cytoplasm becomes 

 clearer and more homogeneous. Then the chromosomes become irreg- 

 ular in shape, lose their individuality and fuse into a single mass, as in 



