Observations and Experiments on the Ctenophore Egg. J 5 



to the right (PL IV, Fig. Gl). Tliis cleavage furrows finally cut 

 off an enucl ;ated portion (PI, IV, Fig. 62). 



j) Kxpcrimeitt X (One case). 



This is a niodification of Exp. VIII. The " cleavage head " 

 was cut in two by a vertical incision, a small nucleated portion 

 was cut off (from the left side of the figure Fig. 63, PL V), and the 

 micromere portion was removed. A new cleavage plane was 

 established at the end of the vertical incision that cut through 

 almost straight. This failed to yield anything of interest, being 

 exactl}^ the same as Figs. 55, 56 (PL IV). 



k) Experiment XI (Eleven cases). 



In this experiment an incision was made in the egg at the 

 micromere pole to see if that would affect the course of cleavage. In 

 nine cases out of eleven the cleavage furrow passed by the incision 

 as though nothing had happened to the egg (PL V,Figs. 65, 67, 68). 

 One notices in Fig. 66 an ectoplasmic accumulation at the left hand 

 corner. In one case the cleavage plane stretched towards the 

 incision and became continuous with it (PL V, Figs. 61. 70 ). In 

 another case the cleavage furrow, which had attained a consider- 

 able length, dwindled owing to the operation, and two new furrows 

 were formed giving rise to a three lobed egg (PL V, Figs. 71, 72, 

 73). As the original cleavage furrow shriveled up, a peculiar ray- 

 like arrangement of entoplasm was seen. Whether it was due to 

 the effect of the incision or to preparation for the formation of two 

 new "heads" I could not determine. At an3^ rate this double 

 " headed " cleavage seemed to be an exceptional case, and should 

 not be taken as of constant occurrence. 



1) Experiment XII (One case). 



Two cuts were made on one egg (Fig. 75 PL V) and the 

 result was as in Fig. 76 (PL V). The cleavage furrow stretched 

 tOAvards one of the incisions and cut through the egg. 



