OK THE GERM CELLS OF METAZOA. 173 



spermatogonia, and none of the cases of spermatogonic monastery in my preparations were 

 sufficiently favorable to allow accurate counting of the chromatin elements. 



In the growth period of the spermatocytes a comparatively small, bivalent chromatin 

 nucleolus, which in the rest stage (N. 2, Fig. 103, PI. Ill) has a peripheral position and 

 rounded form and is not apposed to the true nucleolus (N)- Besides this chromatin 

 nucleolus one or two much smaller, rounded ones can sometimes be seen in the nuclei of 

 the resting spermatocytes, and these stain like the large one with the double stain of 

 Hermann. 



In the nionaster stage of the first maturation division are always found at least seven 

 chromatin elements ; when there are eight the eighth is a small granule (Fig. 105, the 

 smaller of the bodies marked N. 2), and this small element, which frequently cannot be 

 seen at this stage, probably represents one of the minute chromatin uucleoli of the 

 growth period. Of the seven larger elements the smallest, centrally placed one is the 

 bivalent chromatin nucleolus (N. 2, Fig. 104, and the larger of the elements marked 

 N. 2 in Fig. 105) ; this chromatin nucleolus often has its component halves separated 

 (except for a joining linin band) before the period of metakiuesis (Fig. 106). The 

 remaining six elements are chromosomes, and of them four are of approximately equal 

 volume, while one is always much larger and one always much smaller than these four 

 (pole views Figs. 104, 105, lateral view Fig. 106). The five largest chromosomes are 

 clearly dumbbell-shaped on lateral view, and accordingly by analogy with the corre- 

 sponding elements of other Hemiptera may be considered bivalent, even though the 

 number in the spermatogonia was not determined. But the smallest chromosome puzzled 

 me at first with regard to its valence, for it is not more than half the volume of the other 

 five, and sometimes it does not appear dumbbell-shaped, so that I considered the possi- 

 bility of its being uriivalent ; but a careful study of it in numerous cells of the first 

 maturation division resulted in showing in a number of clear cases that it is transversely 

 constricted even before it becomes arranged in the plane of the equator, so that there can 

 hardly be a doubt as to its being bivalent. Fig. 106 shows such a case in an oblique 

 lateral view of the spindle before the chromosomes have become arranged all in one 

 plane, with a well-marked constriction of the smallest chromosome. 



The first maturation division is a reduction division and always halves the six chro- 

 mosomes and the bivalent chromatin nucleolus. 



21. Harmostes reflexulus Stal. 



Thirteen testes of this species were studied. 



In the rest stage of the spermatogonia there are two rounded chromatin nucleoli 

 2, Fig. 107, PL III), of which one or both may be apposed to the true nucleolus (N). 



