CHROMOSOMES IN THE Sl'ERMATOORNESIS OF THE HEMirTEUA HETEROJ'TERA. 1]1 



volumes {JH. 1, ili. 1, Figs. 86-88), and clearly represent the tliinl pair of diplosomes 

 of the preceding prophases ; they are respectively the largest and the smallest ele- 

 ments of the chromosomal plate. Each tetrad is composed of 4 parallel rods, shown 

 in their length in Fig. 80, and from end in Figs. 87, 88 ; their long axes always lie in 

 the plane of the equator. But in the case -of the two dyads, the larger {di. 1) may 

 have its long axis in this ])lane (Fig. 88), l)ut more frequently is inclined to it (Fig. 

 87) ; while the smaller dyad {Di. 1) is composed of two spherules, one on either side 

 of the equatorial plane. All these chromosomes are large, and their parts can be 

 made out with unusual facility. Each of these 10 elements divides so that each sec- 

 ond spermatocyte receives 10, i. e., a portion of each of them. Whether this is a re- 

 ductional or an equational division of the 8 tetrads it would be exceedingly difficult 

 to determine, since each, as in the case of Ascaris, is in the form of four parallel rods ; 

 but I conceive that these 8 bivalent elements differ from those of other Hemiptera 

 only in having their univalent components placed side to side instead of end to end, 

 and that therefore their division may well be, as is certainly the case in the other 

 Hemiptera, reductional. A pole view of one daughter chromosomal plate in the 

 early anajjhase is shown in Fig. 89 ; here are 8 bipartite elements, the daughters of 

 the former 8 tetrads, and 2 unipai'tite ones {I)i. 1, di. 1), the division products of the 

 2 earlier dyads. 



Second Maturation Mitosis. — The 8 l)ipartite elements, which are 6 autosomes and 

 2 of the diplosomes, take positions with their long axes in the plane of the equator 

 (Figs. 90, 91), and all of them divide so that the components of each become separated 

 into opposite spermatids ; this is probably an equational division. But the unipartite 

 diplosomes Di. 1 and di. 1 never lie in the equator, but one is always near one spindle 

 pole and the other near the opposite pole ; this was invariably the case with every one 

 of these stages found. Accordingly, the smaller diplosome, Di. 1, passes wholly into 

 one spermatid, the larger diplosome, Di. 1, into the other spermatid. Fig. 92 shows 

 the chromosomes of a spermatid that has received the smaller one, and Fig. 93 a sper- 

 matid that has gotten the larger, these diplosomes being recognizable among the other 

 chromosomes by their form as well as by their deej^er stain. 



In the spermatocytes there are accordingly 6 autosomes that divide in both ma- 

 turation mitoses ; 2 probably bivalent diplosomes each of which divides as do the 

 autosomes ; but one pair of diplosomes, that one characterized by very unequal com- 

 ponents, each component dividing separately (so probably equationall}') in the first 

 mitosis, but their daughter products, without conjugating, passing without division 

 into opposite spermatids in the second mitosis. 



The 6 quadripartite autosomes are probably, by analogy with the phenomena of 



