INITIATION OF DEVELOPMENT IN CHLETOPTERl S. 4! 



eggs may be seen 24 minutes after being removed from the heat, 

 containing two nuclei and with no polar bodies. These nuclei 

 appear to unite in certain eggs. Other eggs may be seen with 

 one polar body and one nucleus. There were not many eggs in 

 which a count of the chromosomes could be made, but in one such 

 count there appeared to be 18 chromosomes. Evidently tin- 

 second polar nucleus if formed at all had united with the egg 

 nucleus. I think, however, that the second polar spindle fre- 

 quently is not formed, but that the chromosomes may go into 

 the resting stage after the first maturation spindle, and emerge 

 from this in the characteristic rod shape of the cleavage divisions, 

 whether one or no polar body has been extruded. 



Cleavage proceeds with more or less regularity. Unfortu- 

 nately the eggs were killed at such time that only one egg was 

 caught with the spindle of first cleavage. It seems to be in early 

 anaphase, and although I cannot count the chromosomes exactly, 

 owing to their twisted rod shape and the direction of the section, 

 their number was approximately 36, which makes it seem that 

 the number normal for cleavage, 18, is probably present in each 

 half of the spindle. Second cleavage stages are wanting also, 

 but eggs fixed two hours from the beginning of the experiment 

 show the four-cell stage with spindles of third cleavage (cf. 

 Fig. 9). In one egg in which I was able to count the chromo- 

 somes there appeared to be 18 in each cell. (As before stated, 

 the count is not exact, and only serves to indicate whether the 

 chromosome behavior as to numbers, in these mitoses, is proceed- 

 ing approximately after the normal order.) At this time many 

 eggs are still seen in the metaphase of the first maturation spindle. 

 This spindle often lies in the center of the egg instead of at the 

 periphery, but is easily distinguished from the cleavage spindle 

 by its smaller size and by the chromosomes, which are in the 

 maturation form. A number of eggs are unsegmented and have 

 multipolar spindles, others are segmented abnormally. Many 

 appear to be developing after the characteristic KC1 fashion. 



Later sections, between 6 and 7 hours, show many segmented 

 blastulae (Fig. 10). The blastulse swim at about this time. 

 Abnormalities are usually to be seen; some larvae have almost 

 no segmentation cavity, others small extra-ovates. The arrange- 



