JOURNAL OF THE COLLEGE OF SCIENCE, IMPERIAL UNIVERSITY, 

 TOKYO, JAPAN. 



VOL. XXVII., ARTICLE 10. 



Experiments on Cleavage in the Egg of 

 Cerebratuliis, 



By 



Naohide Yatsu. 



Introduction 



Unconscious of Zeleny's work on tlie nemertine egg ('04), 

 which bad been carried on a few mouths before at Naples, I 

 took up a similar problem in the summer of 1903 at South 

 Harpswell, Maine and nrrived at results ('04) which agree in 

 tbe main wnth his. However, as regards the cleavage factors 

 incidentally described in my paper, some difference is found 

 between his results and mine. In order partly to clear up the 

 discrepancy and partly to promote our knowledge of cleavage- 

 physiology, more experiments were made upon the Qgg of both 

 Cerebrotulus lacteus and 61 marginatus in the summers of 1904, '05 

 and '07 at the Harpswell Laboratory, and in the spring of 1906 

 at the Naples Zoological Station.^ In the present paper I shall 

 deal with the results attained from those experiments and the 

 conclusions to be derived from them. 



1 The work of the year-; 1905 and 'GO was carried out on a grant from the Caknegie 

 Institution of Washington. My best thanks are due to Professor .1. S. KiNGSLEY of the 

 Harpswell Laboratory and tn tlie late Professor A. DoHRX and the stafl' of the Naples 

 Zoological Station. 



