CHROMOSOMES IN EMBRYOS. 47 



the matured egg he found to be eleven. The chromosomes in 

 the reduced groups, either in the polar body or the egg, showed 

 the same relative size differences as the corresponding pairs in 

 the oogonia, and the chromosomes in the matured ova correspond, 

 in general, to those of a sperm bearing the .r-chromosome. The 

 chromosome groups, which were counted in the embryonic mitoses 

 of Anasa were from incomplete blastoderm stages. The embryos 

 were found to be of two kinds: one containing twenty-one chro- 

 mosomes, the other twenty-two. One case was reported of 

 twenty-three chromosomes, but this Morrill suggests may be 

 due to an accident in technique. The two different chromosome 

 groups, those having twenty-one and twenty-two, correspond, 

 respectively, to the groups found in the spermatogonia and the 

 oogonia. There are the same size differences, and the same 

 number of macro- and microchromosomes. He states that the 

 chromosomes in general are more elongated in the embryonic 

 mitoses than in those of the germ cells, which makes the task of 

 pairing them extremely difficult, if it is at all possible, except in 

 the case of the macrochromosomes and the two w-chromosomes. 



The results, which the present report embodies, were obtained, 

 in the case of Anasa, from a study of the somatic mitoses in 

 several stages of development. Although mitoses are abundant 

 in all the tissues of the embryos, few are sufficiently favorable 

 for even tentative counts, still fewer for actual counts. In no 

 case has it been possible to obtain more than seven counts from 

 one individual, while three counts are more nearly the average. 

 The chromosomes, especially in the metaphase groups, are 

 crowded together, and the possibility of counting them at all 

 depends chiefly on the extent of destaining. 



At first some rather startling results were obtained. Some 

 counts revealed a number as low as fourteen chromosomes in one 

 plate, while others ran up to twenty-four in number, and there 

 seemed to be no number characteristic of any one tissue, though 

 the average varied around eighteen and twenty. When, however 

 a large number of series was examined, and the exact point of 

 optimum destaining was acquired, the results tabulated showed 

 that the seemingly aberrant counts were wrong, and that they 

 might be due to any of the following reasons; (i) counting early 



