Volume IV. January, i8gi. Number 3. 



JOURNAL 



OF 



MORPHOLOGY 



STUDIES ON CEPHALOPODS. 



I. 



Cleavage of the Ovum. 



S. WATASE, 

 Clark University. 



CONTENTS. 



PAGE 



I. Introduction 247 



II. Remarks on the Animal Ovum 250 



III. Relation of the External Phenomena of Cleavage of the Ovum to the Inter- 



nal Phenomena or Caryokinesis 256 



IV. Cleavage of the Ovum of the Cephalopod, Loligo Pealei, Lesueur 278 



V. Remarks on the Variation of Cleavage in the Cephalopod 289-294 



I. 



In the following pages, I will first attempt to treat the general 

 morphology of the animal ovum from the standpoint of some 

 embryological and morphological facts and theories. In the 

 next place, the relation of the external phenomena of cleavage, 

 as shown by the behavior of the cytoplasm, to the internal 

 phenomena of nuclear cleavage or caryokinesis will be dis- 

 cussed. In this connection, some theories on caryokinesis will 

 be examined, my interpretation of the cleavage phenomena 

 being that they are essentially the analysis of the potential 

 tissues contained in the cleavage nucleus, and that caryokinesis 



247 



