CHROMOSOMES IN COREID HEMIPTERA. I O/ 



for these groups correspond in number and size-relations with 

 those of the spermatogonia and oogonia respectively. Like 

 .1 nasa again, the male groups contain three chromosomes which 

 are distinctly larger than the others (Fig. 10, a-f and h), one of 

 ilu-m probably representing the unpaired idiochromosome. In 

 the ft -in. ilc Croups four largest chromosomes can frequently be 

 di-tinv:iii-hed (Fig. II, b, c and/), though they cannot be identi- 

 fied in all the figures, probably on account of fore-shortening. 

 Two of the-e may be considered as the paired idiochromosome-. 

 in plan- of the unpaired element of the male groups. The m- 

 ( -hromo-oiMi - are typically paired elements of both male and 

 fcin. tli ^nuipx. All the chromosomes as in Anasa are more i-lon- 



<1 tli.in in the gonads but still preserve the same size-relations. 

 Tin groups -hown in Figs, 10 and 11 were selected from a large 

 number of clear preparations. Fig. 10, /, is a group of 22 chromo- 

 somes taken from an embryo in which all other counts gave 21. 

 I or t hi-, tin- single exception of its kind observed, it is difficult 

 ic. give .1 -aiisfaclory explanation, though the same possibilities 

 Mii^r-trd in connection with the exception found in Anasa (vi<l. 

 page i"-' mil i also apply here. There were no neighboring 



ip- In. m which the extra chromosome could have been de- 

 rived. 



4. rrotcnor belfragei. 



The mil T\ >nic mitoses of this species are not quite so favorable 

 for making chromosome counts as those of the two preceding 

 form-, on a.voimt of the elongation of the chromosomes in the 

 rail\ ami even late cleavage stages. In the blastoderm stage 

 tin rliromo-omes arc more compact, but very few embryos were 

 obtained at this time so that the results are very meagre. Fig. 

 u -ho\\- t\\o [^-chromosome groups (a and b) taken from an 

 Ma-todcrm stage, and one 14-chromosome group (c) from 

 i-mbryo in the same stage. 



In tlu- i .^-chromosome groups (Fig. 12, a and b) a very large 

 chrom.i-.onu-. unquestionably the unpaired idiochromosome, 

 Man.l> out cli-arly, being more than twice as large as any other. 

 A . .nd laixr-t pair can also be readily identified and a smallest 

 pair, tin- rn-chromosomes. 



