lOS CHROMOSOMES IN THE SPERMATOGENESIS OF THE HEMIPTERA HETEROPTERA. 



nients marked K and x of Figs. 61-63, and the elements Z and Y of the spermato- 

 gonium (Fig. 59). 



Second Maturation Division. — On pole view of the spindle (Plate X, Fig. 67) are 

 seen 7 chromosomes, the central one of which is bivalent and represents the two larger 

 diplosomes placed end to end as lateral views evince (Fig. 66, Di, di); this bivalent 

 chromosome divides reductionally, the 6 autosomes probably equationally. In the 

 spermatids (Fig. 68) there are always 7 chromosomes, half of the spermatids containing 

 tlie larger and half the smaller component of the larger diplosome pair. 



Literature. — My previous account was entirely correct, except that I failed to note 

 that the larger diplosomes divide equationally in the first maturation mitosis. Wilson 

 (1905o.) described the second maturation mitosis correctly, but could not follow the 

 history of the smallest diplosomes any more satisfactorily tlian I have been able to do 

 in either of my accounts. 



11. EURYGASTER ALTERNATUS Say. 



Growth Period. — There are two diplosomes of very different v<jlumes {Di, di, Plate 

 X, Fig. 69) ; this figure shows also three whole bivalent autosomes. In the earlier 

 period these are usually, not always, placed end to end. Each is at first elongate, in 

 the postsynapsis undei-goes a split through its length, and for a considerable time retains 

 this fissure in this position ; later each half of each diplosome rounds up so that the 

 whole appears to be transversely constricted, but this constriction is the same as the 

 earlier split. There is no complete rest stage. 



First Maturation Division. — There are always 7 chromosomes (Fig. 70) ; the two 

 smallest {Di, di) are the diplosomes that come to lie separately- in the equator and 

 divide equationally ; their precise location in the chromosomal plate is vai-iable. The 

 others are 5 bivalent autosomes that divide reductionally as may be ascertained with 

 great certainty from the examination of the earlier stages ; and when seen from the 

 fiat surface each shows the longitudinal split parallel to the long axis. In the succeed- 

 ing anaphase this split opens up as in the other Hemiptera. 



Second Maturation Mitosis. — Pole views (Fig. 72) show apparently only 6 chromo- 

 somes, but the central one is really Ijivalent, composed of the two diplosomes {Di, di) 

 placed end to end ; a lateral view shows this bivalent element more distinctly (Fig. 

 73). The diplosomes divide reductionally, the autosomes equationally, so that each 

 spermatid receives 6 elements. 



Though there were no spermatogonic mitoses upon my preparations, there can be 

 little doubt that the chromosomes there would consist of 10 autosomes and 2 diplosomes. 



Literature. — My previous very brief account was correct so far as it went. 



