CHROMOSOMES IN THE SPERMATOGENESIS OF THE HEMIPTERA IIETEROI'TERA. 107 



somes, while two remaining elements of veiy unequal volume {Di, di) are probably 

 correspondent to the two larger diplosomes of the later stages. The minute body 

 lettered Z is probably another diplosome and so also the one lettered V. All the chro- 

 mosomes are characterized by rather uneven and irregular outlines. 



Growth Period. — Twelve autosomes unite to form 6 bivalent ones as shown by 

 the phenomena of the subsequent propha.ses. The two larger diplosomes [Di, di, 

 Figs. 60-63) usually lie close together in the earlier growth period, but separate from 

 each other either soon after or else not until the late prophases. When in contact 

 their long axes may be parallel, but moi'e usually they are crossed. At an early stage 

 each becomes distinctly split along its length, but this usually closes soon after it 

 becomes well marked, which is associated with the phenomenon that each di^Dlosome 

 swells in size and becomes more spherical ; just before the following mitosis this split 

 reappears on each as a transverse constriction. Besides these two larger diplosomes 

 more minute ones are to be seen during the growth period, and despite their small 

 size may be easily distinguished by their deep stain from the pale autosomes. It is 

 very difficult to decide exactly what their number is, though in most cases 3 or 4 such 

 bodies can be found. Generally two minutest ones of equal volume [K, Figs. 61, 63) 

 lie upon the surface of the largest plasmosome {PI), while 1 or 2 slightly larger ones 

 (.(•, Figs. 62, 63) are situated elsewhere in the nucleus and sometimes in contact with 

 smaller plasmosomes. The 2 smallest, those upon the largest plasmosome designated 

 by the letter K, are always close together and of equal size, therefore they are prob- 

 ably (longitudinal ?) division products of a single one ; while the two others are 

 usually widely separated and of unequal size. These four smallest diplosomes of the 

 growth period may be represented by three minute elements in the spermatogonium : 

 we found in that stage (Fig. 59) one minute element {Y) and another probably separ- 

 ate element (Z), and there might be still another in this chromosomal plate but hidden 

 from view. Accordingly, judging from the phenomena of the growth period, there 

 must be at least 4 diplosomes represented in the spermatogonium, that is, a total of 16 

 chromosomes, if not indeed 5 diplosomes. 



First Maturation Mitosis. — There are always' at least 8 distinct elements in the 

 spindle, which are: 6 l)ivalent autosomes of very different volumes {A, a-F, f. Fig. 

 65) which undergo a reduction division ; and two univalent diplosomes {Di, di) which 

 divide presumably equationally, and represent the diplosomes so lettered in the pre- 

 ceding stages. The minute diplosomes are rarely found in the equatoi'ial plate, but 

 in two cases, one of them shown in Fig. 64, a pair of small bodies {x) placed close 

 together were found ; they do not apj^ear to divide with the other chi-omosomes and 

 seem afterwards to move out intu the cytoplasm ; they may represent the small ele- 



