10 PAULINE H. DEDERER 
autosome which has separated from it during division, since 
in anaphase a small chromatin mass lies near one end of the 
large chromosome as if detached from it. Second divisions were 
not observed but Seiler believes they are probably equational. 
He suggests the tentative interpretation that the extra small 
chromosome is the X chromosome. Unfortunately, only polar 
views of the first division are given, and these only of late 
anaphase, so it is impossible to determine how the extra 
chromosome arises. It is possible that the separation of this 
chromosome (described by Seiler) may be merely a temporary 
condition, followed by a union with the large one at the second 
metaphase, thus giving similar groups of chromosomes in 
all the oocytes. In view of the fact that in echinoderm eggs an 
apparently clear case of dimorphism has been found to be 
incorrect, it seems particularly necessary’to scrutinize carefully 
any evidence along this line. ° 
EARLY OOGENESIS 
A study of the early oogenesis of P. cynthia was undertaken 
in order to determine the origin of the haploid groups of chromo- 
somes which enter the first polar metaphase. By analogy with 
spermatogenesis, pairing of the chromosomes in the egg should ° 
occur before the growth period. Although the material is un- 
favorable for the study of oogenesis as a whole, a seriation of 
stages was obtained, and several points of interest were ob- 
served in regard to the differentiation of primitive ovarian cells 
into eggs and nurse cells, and their later relation to each other. 
1. OBSERVATIONS 
a. Growth of the ovary: General description 
The earliest ovaries obtained were from larvae fixed the latter 
part of August, a few days before the spinning of the cocoon. 
They are pear-shaped bodies, about 1 mm. in length, slightly 
smaller than a mature egg. Figure 29 is a lengthwise section 
through a larval ovary. The oval mass of connective tissue 
surrounds four egg strings which take a complicated course 
