CHI i.MES IX COREID HEMIPTERA. I I/ 



I .\chxling the early cleavage groups mentioned above, a num- 

 ber ') authors have described the chromosomes of older somatir 

 < 11-. II. nking ('92) found the number of chromosomes in the 

 fnllii It- and connective tissue cells, of Pyrrhocoris to be 24. 

 I' . it^ch ('oi) observed that young blastoderm-cells of 



tlif l'f tin multiple groups. Miss Stevens ('05$ and '066) 



df-cribed the somatic groups of several species of Coleoptera 

 .nxl l< 'inxl i hat the small idiochromosome which occurs only in 

 tlif malt n! ihf-e forms could be readily identified. Yon Bachr 

 '1 that the male somatic groups of Aphis saliceli 

 aiii 5 hromosomes, one less than the female. Gutherz (' 

 liidfl Mi.it in Gryllus domesticus the somatic cells have the 

 -aim- iniiiil.fr of chromosomes as the oogonia and spermatogonia 

 though his obser\ - ations on this point were not very 

 nxl no figures of somatic mitoses were given. Don- 

 bserved the somatic groups in the male and female 

 I nil if gall-fly. He found that in the male, some somatic 



mil. I-M - -li.\\ thr diploid number oi chromosomes while others 

 lx>\\ the haploid number. In the female, all somatic 

 mill i -i - lia\c the diploid number. The very anomalous condi- 

 tion- di -. liU-d for the male do not at present rest upon dcmon- 

 Btrative < \xlence as the chromosomes were found to be small 

 .nxl diitii ult to count. In addition to the above-mentioned ob- 

 servations, most recent papers on the spermatogenesis of insects 

 (i 'iiiain ai i < 'iints of the oogonial groups in which idiochromosomes 

 can I'tii- n he identified. 



1 i. mi iln luregoing brief view of the literature on the chromo- 

 M.iiif- in .... genesis and cleavage, it is evident that with the'excep- 

 t inn "I Mi Elevens and Morgan none of the authors have traced 

 tin iilii.t Im-mosomes into the cleavage and later somatic mitoses, 

 and ix 'in but Miss Stevens, Morgan and von Baehr have sho\\n 

 that tin embryonic or larval somatic cells of male indi\xluaU 

 tliltt i limn those of females in the number or size of their chromo- 

 somes. Morgan h.is also shown that idiochromosomes are pres- 

 ent in tin- ]>. -lar spindle where, in his material, they behave in .1 

 characteristic manner. The results on the whole show, 1 think, 

 that idii -chromosomes ("heterochromosomes") are constant chro- 

 nx-omc-flcmeiits and not merely temporary structures (nucleoli) 

 (luring maturation. 



