CHROMOSOMES IN THE SPERMATOGENESIS OF THE HEMIl'TERA HETEROI'TERA. 123 



compact and shorter, and though they are usually near together appear never to 

 actually conjugate ; and the 5 hivalent autosomes shorten and condense into short 

 tetrads. 



In the spindle the diplosomes never form a bivalent element in the equator Ijut 

 always lie on either side and at some distance from this plane {Di,dl, Fig. 19U). A 

 pole view of the equatorial plane shows, accordingly, only 6 chromosomes (Fig. J 89), 

 which are the univalent monosoine [Mo], recognizable by its lesser depth, and 5 auto- 

 somes ; the constrictions seen on end views of the latter are their longitudinal splits. 

 The monosome is a dyad, while the autosomes are tetrads, as shown on lateral views 

 (Fig. 190). In the anaphase (Fig. 191) each daughter cell receives one of the diplo- 

 somes {l)i, di), a half of the monosoine (J/o), while the 5 autosomes divide reduction- 

 ally and their daughter components as they sej^arate show each the reopening longi- 

 tudinal split. 



Second Maturation Mitosis. — Pole views (Fig. 192) of the spindle show 7 elements 

 all in one plane ; the smallest is a diplosome {Di) while the monosome {Mo) may be dis- 

 tinguished from the autosomes by its lesser depth ; a lateral view of the same stage is 

 given in Fig. 193, where the monosome is readily marked by its unconstricted form. 

 Each of the autosomes divides equationally and so does the diplosome. But the 

 monosome passes without dividing into one of the spermatids {Mo, Fig. 194). A pole 

 view of any spermatid shows a circle of 5 autosomes around a minute central diplo- 

 some (Fig. 195) : and half of the spermatids show just beneath this chromosomal plate 

 a monosome. 



Litcvatwc. — I had described (190 HO this .spermatogenesis in the main correctly, 



only I failed to decide whether what I called the "odd chromosome" divided in the 



second maturation division and failed to notice that it is the larger allosome of the 



growth period ; but later (1905) I showed that the monosome does not divide in this 



mitosis. 



26. Oncoi'eltus fasciatus Dall. 



My preceding account, a rather detailed one, of the spermatogenesis of this species 

 was entirely cori-ect. Of the 16 chromosomes of the spermatogcmia I demonstrated 

 that 2 are diplosomes, that these are distinguishable during the growth period, and 

 very frequently separated from each other there, and that they enter the chi'omosomal 

 plate of the first maturation mitosis separately and that each divides by itself All 

 that is to be corrected is my former interpretation that each of these is in the sperma- 

 togonium already bivalent, and that the division of each in the spermatocytes is to be 

 considered reductional ; nuw I lind no good reason for such a view, and judge the 

 latter division to be an equational one of the diplosomes. There is to be added to 

 that former account the description of the 



