Observations on Fresh-water Polyzoa. 



(Pectinatella gelatinosa, nov. sp.) 



by 



A. Oka. 



Iiuperia] University, Tokyo, 

 with Plates XVII— XX. 



The pi'csent paper emborlies the results of my investigations on 

 a new species of Fresli-water Polyzoa that lives in a large pond in 

 the grounds of the Imperial University, Tokyo, and is published with 

 the hope that it may throw some light on certain points in the 

 structure and development of the order Phylactolaemata, which have 

 hith('rf(^ remained ol)scure in spite of many efforts of former investi- 

 gators. The researches were begun, in the spring of 1888, at the 

 suggestion of Prof, [, Ijima, and I am indebted both to him and to 

 Prof. K. Mitsukuri for useful advice. My thanks are also due to 

 Mr. S. Watase, now of the flohns Hopkins University, who, while 

 here some years ago, studied the same species, for kindly sending me 

 his drawings showing the formation of the statoblast. 



Altliough the species which I have studied does not agree in some 

 points with the generic description of Pectinatella in Hyatt's Observa- 

 tions (5), it can belong to no other genus. The statements given 

 there were made when only one species, viz Pect, magnifica, was 

 known, and must certainly be modified to receive the new one. The 



