CHROMOSOMES IX COREID HEMIPTERA. 115 



more recently ' '09) she has abandoned this view and has reached 

 conclusion-, in agreement with those of Morgan and von Baehr, 

 mtntioned U-luw. The results of Tannreuther ('07) on the 

 maturation and cleavage of several species of aphids differ in 

 many important respects from those of other workers on the 

 same group. They have been questioned by Morgan ('09) and 

 'on Bat-In '09) and will not be considered here. Morgan ('08 

 ind '09 has traced the full history of the chromosomes through 

 .m rations of phylloxerans. He observed that the par- 

 -. -iii-tic eggs of the second generation, i. e., those which 

 . r the sexual individuals, are of two sorts both as to their 

 and tin- number of chromosomes in the embryos which they 

 produce. The male embryos have actually two less chromo- 

 somea than the female though this difference is not always ap- 

 parent o\\ing to fusions occurring between certain chromosomes 

 i tin- "ai --ones.") The- embryonic chromosome-groups of fe- 

 male indis idtials contain four "accessory" chromosomes. Those 

 <il tin- malt -, however, have but two "accessories" since although 

 malt- an- produced parthenogenetically from females, two of 

 tin -< chromosomes are given off to the polar body in the matura- 

 tion < -I t In- male-producing egg. The most important conclusions 

 to IK iliaun In mi these results for our purposes are, that idio- 

 rl Mom. - are present throughout the entire life-cycle- and 

 that it i- |>o--ili|e to diagnose the sex of an embryo by counting 

 it- t hi 01 no -mnes, though here it is true, sex is also associated 

 \\ith t! of tin- egg. Yon Baehr ('09) described the matura- 



tion and ( lea\agc of the parthenogenetic eggs of several species 

 ot aphid-. Hi- results were in general similar to those of Miss 

 Ste\cii-, the maturation and cleavage mitoses being similar in 

 tin- number and size relations of the chromosomes. He did not 

 obsen < an\ elimination of "accessory" chromosomes in the polar 

 di\ i-ii-n i-t" male eggs as in the phylloxerans. However, in one 

 maturation -pindle of Aphis saliceti (loc. cit., PI. XIV., Fig. 42) 

 hr ligute- 5 chromosomes, the remaining figures showing 6, and 

 in a male -omaiic cell i.1'1. XV., Fig. 94), as well as in the sperma- 

 to-<,nia. 5 chromosomes again appear. Moreover his results on 

 the -permato-eiie-is of Aphis salicdi as well as those ot Mi-- 

 ('09) on the spermatogenesis of other aphids would seem 



