CHROMOSOMES IN THK SPERMATOGENESIS OP THE HEMIPTERA HETEROPTERA. 133 



in l)otli form jiiid volume ; but the very smallest (Mo) has no mate in size, ami is 

 therefore a monosome. 



Growth Penod. — This terminates in a complete rest stage (Fig. 260). There is a 

 large plasmosome (/''/) attached to which is either a single body or a pair of bodies of 

 like volume {Mo) ; the latter condition is to be explained as a monosome divided equa- 

 tionally into two {)arts, because these later join to compose the mon(jsome of the 

 maturation mitoses, and more particularly because in the earlier growth period these 

 are represented by a single one. This monosome, respectively its halves, swells con- 

 siderably in size during the growth period, and while continuing dense it does not 

 remain safraninophilous. No bodies were found that represented diplosomes. 



First Maturation Division. — In the prophases the plasmosome disappears ; Fig. 261 

 reproduces a late prophase and shows all the chromosomes. Each autosome is bivalent, 

 composed of 2 univalent ones placed more usually end to end, more rarely side to side, 

 and each univalent element when viewed from its flattened surface shows a split along 

 its axis which is evidently the same as the earlier longitudinal split of the postsynapsis 

 stage. This split gradually closes, though never completely, as the autosomes con- 

 dense and retains its position parallel to the length of the autosome. Besides these 

 autosomes there are 2 much smaller bodies {Mo), which are alike in size and each, so 

 far as 1 could determine, is unipartite ; at tliis stage they are frequently not separated 

 but apposed, and probably represent the halves of the monosome. 



Pole views of the equatorial plate (Figs. 266, 267) show 11 elements, one more 

 than half the numljer in the spermatogonium ; on strict pole view 10 of them, the 

 autosomes, always seem bipartite, while the smallest one, the monosome [Mo], appears 

 unipartite; seen from the side (Fig. 262) the 10 autosomes are found to be tetrads, 

 while the monosome {Mo) is a dyad. This monosome divides and apparently through 

 the 2)lane where its halves had previously come together, therefore equationally. The 

 10 tetrads, the bivalent autosomes, are so nearly quadi-atic in outline that it is diffi- 

 cult to decide how they divide, but there is no reason to hold that they do not divide 

 reductionally. As a result each second spermatocyte receives also 1 1 elements. 



Second Maturation Division. — The chromosomes evince no great constancy in 

 their arrangement in the spindle (Figs. 266, 267), the monosome may be recognized 

 by its lesser depth {Mo). Side views (Fig. 265) show that 10 are always bipartite with 

 their constrictions placed in the equator; these are the autosomes and there can be no 

 question that all of them divide. But the smallest element, the monosome {Mo), is 

 spherical, and placed usually a little above or below the plane of the autosomes ; I 

 have not drawn its mantle fiber attachments because I was unable to ascertain them. 

 Only one clear pole view of a daughter plate of chromosomes of this mitosis was seen 



