/ 

 JOURNAL OF THE COLLEGE OF SCIENCE, IMPERIAL UNIVERSITY, 

 TüKYÜ, JAPAN. 



VOL. XXL, ARTICLE 11. 



On the Gastiulation in Petromyzon. 



By 

 S. Hatta. 



Professor of Zoology and Eiiibrjjologij in the 

 Sapporo Agricultural College. 



With Fiâtes I.-llI. 



In a former paper/^ I dealt with the gastrulation of the 

 ovum in Petromyzon, but owing chiefly to the want, at that time, 

 of the living material at my hand, my sketch was necessarily 

 incomplete. Since that time, I have had several opportunities 

 to renew the observation ; especially during the last spring, an 

 unusually abundant supply of the material enabled me to carry 

 on my work on this subject more satisfactorily than it had ever 

 })een possible. Unlike Tokyo, my former residence, there is in 

 Sapporo a number of bodies of water in which the animal lives ; 

 it runs up in crowds rivers and brooks in and about the city to 

 spawn in the sandy beds of these streams and also of springs. 

 This circumstance induced me to try the artificial fertilization of 

 ovum repeatedly, and I am glad to say the experiment was 

 always attended with success. The material obtained in this way 

 was sufficient for following the steps of changes undergone by the 



1) On the Formation of the Germiniil Layers in Petromyzon. Jour. Coll. Sc, Imp. 

 Univ., Tokyo, Japan. Vol. V., Pt. I., 1891. 



