3o6 



Charles Zeleny. 



None of the three larvae which were allowed to develop showed 

 a sufficient differentiation of parts to be of service in determining 

 the localization of the morphogenic factors at this stage. The 

 one figured (8H) is a large blastula, the cavity of which is filled 

 with free spherical cells. The other two larvae, one of which was 

 just mentioned above, both developed after extremely irregular 

 cleavages, and are interesting because they show the presence of 

 an extremely high power of regulation. However, because of the 

 lack of data as regards their structure no definite conclusion can 

 be drawn even here. 



IV. Second polar body to beginning of lateral elongation of 

 the egg. The period is limited on the one hand by the complete 

 separation of the second polar body from the egg and on the 

 other by the division of the cleavage nucleus and the accompany- 

 ing elongation of the cell preparatory to the first cell division 

 (Fig. 9). Eleven eggs were operated on, four by horizontal. 



V 



Fig. 9 (x 180). 

 Diagram of Egg zvith Tzvo Polar Bodies. 



The basal protuberance has disappeared; HH, VV and OO represent, 

 respectively, the directions of the horizontal, vertical and oblique cuts. 



four by vertical and three by oblique cuts. The fragments do not 

 segment as wholes, but shotv very evident departures from that 

 mode. However, there is a wide difference in the extent of this 

 departure in different cases. As determined by the experiments, 

 the range of the variation is from a possible whole cleavage, 

 through cases with a slight disturbance in size and position of 



