14 



ART. 17. — N. YATSU. 



Series G. Cutting Experiment during ths First Cleavage. 



The blastomeres were separated by a vertical cut at various 

 stages of constriction during the first cleavage (Fig. 11 a). 

 Fourteen pilidia were obtained. 



Group A (operation was performed 

 when the connection of blastomeres 

 was broad. 



(8 perfect. 

 2 defective. 

 Group B (operation was performed 

 when the the blastomeres were 

 connected by a narrow bridge). 



{2 perfect. 

 2 defective. 

 The cases are not numerous enough 



A, pilidiura produced by ^o enable us to draw any conclusion, yet 

 the vertical cut a. . . 



it is certain that quite contrary to a 



single case described in my previous paper ('04 p. 132), the 



resulting pilidia from this operation bear strong resemblance in 



general appearance to those obtained by the isolation of the 



2-cell stage, that is, the apical organ is usually found somewhat 



shifted to one side and the development of the lappets is retarded 



as is shown in Fig. 11 A. 



Series H. Isolation Experiment at the 2-cell Stage. 



Fig. 11. 



Blastomeres Avere isolated from each other at the 2-cell 

 stage either by cutting with a knife or by means of Ca-free 

 sea-water. 



