Il6 CHARLES V. MORRILL. 



to indicate that the behavior of the chromosomes in the female 

 line is probably similar to that in phylloxerans. 



Hemiptera-heteroptera. The only observations on the matura- 

 tion and cleavage of the egg in this group are those of Henking 

 ('92) on Pyrrhocoris. He has given a very extensive and detailed 

 account of the chromosome history in this form and in a previous 

 paper ('91) described the spermatogenesis. He found that in the 

 diploid groups of the oogonia, there were 24 chromosomes. The 

 follicle and connective tissue cells, both larval and adult also 

 showed this number. In the haploid group of the first polar 

 spindle 12 dumbbell-shaped chromosomes appeared. In one such 

 group ('92, PI. III., Fig. 83) one chromosome is much larger than 

 the rest and is probably the idiochromosome pair (cf. Wilson's 

 ('O9</) figures of the oogonial groups). The second polar spindle 

 showed again 12 dumbbell-shaped chromosomes. The number 

 of chromosomes in the male and female pronuclei was not ac- 

 curately determined but in Henking's Fig. 90 (PI. III.) one such 

 nucleus shows 12 chromosomes. The early cleavage spindles 

 were figured but of them the author says (loc. cit., pp. 29-30): 

 "The number (of chromosomes) cannot be accurately determined 

 on account of the smallness of the spindle and the close grouping 

 of the chromosomes ... it should be 24." He thus did not 

 distinguish two classes of embryos with reference to the chromo- 

 some number. This, no doubt, was partly due to the fact that 

 he had not observed any difference in the number of chromosomes 

 in the spermatogonia and oogonia and did not appreciate the 

 significance of the idiochromosome ("accessory" chromosome) 

 which he himself was the first to describe. Foot and Strobell 

 ('09) have described the growth period of the oocytes of Euschis- 

 tus variolarius. In accordance with the earlier account of Wilson 

 ('06), they find no chromatin nucleolus in the young oocytes or 

 germinal vesicles of this species but in the older oocytes and in 

 the germinal vesicles there is a relatively large achromatic nucleo- 

 lus. The maturation divisions were not described. 



Arachnida. Montgomery's ('07) results on Theridium are not 

 very extensive from the chromosome-standpoint. He found in 

 the second polar spindle 12 chromosomes and in a fourth cleavage 

 spindle 24 chromosomes. No idiochromosomes were <>li-rrved. 



