62 



PROTOPLASMIC CONSISTENCY AND CELL DIVISION 



place in the unsegmented Chatopterus embryos experimentally pro- 

 duced by Lillie.^ 



Experiment 4. — (Fig. 9.) Fig. 9 a to e depicts the case of an egg 

 with the cleavage furrow just beginning in which the diagonal cut 

 was incomplete so that the two pieces remained connected at one 

 end of the cut. The original furrow persisted for a time during which 

 it deepened considerably. 30 minutes after the cut had been made 



4-.4-5 



s.oo 



Fig. 9. Effect on an Asterias ovum of a deep cut which did not persist, a, 

 operation performed at 4.10 p.m. b, c, and d show the egg respectively at 4.24, 

 4.40, and 4.45 p.m. Both the cut and the cleavage furrow disappear together 

 with a reversal of the ovum from a semisohd to a more fluid state, e, 5.00 p.m., 

 the ovum has divided into four normal blastomeres. (The ovum developed into 

 a normal embryo.) 



no sign of astral radiations were present and both the original seg- 

 mentation furrow and the cut produced by the needle were being 

 obliterated (Fig. 9 c and d). At 5 p.m. the egg had divided into 

 four apparently normal blastomeres (Fig. 9 e) and was only slightly 



^ Lillie, F. R., Observations and experiments concerning the elementary phe- 

 nomena of embryonic development in Chcetopterus, J. Exp. ZooL, 1906, iii, 153. 



