Notes on the Cephalopoda. 



By 



Mad oka Sasaki, 



College of Agriculture, Sapporo. 



I. On the male of Amphitretus pel amicus Hoyle. 



Prof. A. Oka obtained in Tateyama Bay, Sagami Sea, April 7th, 1910, 

 a jellyfish-like octopod which I identify as Amphitretus pelagicus Hoyle". 

 So far as I know, it is the second specimen of the species captured in the 

 region, the first being the one which was described by Ijima and Ikeda s) . 

 Moreover, it is of special interest as being the first specimen ever obtained, 

 which can be determined as the male of that rare species. According to 

 the statement of the collector, the specimen in question was discovered 

 among the rocks near the shore after a storm. It is preserved in an ex- 

 cellent state. For placing this valuable specimen at my disposal, I wish 

 here to express my grateful thanks to Professor Oka. 



Aside of the characters in relation to the difference in sex, the specimen 

 is not without some noteworthy differences from the female described by 

 Ijima and Ikeda. But this may be due in part simply to the difference in 

 the state of preservation and in part to variations of secondary importance. 

 (In making comparisons, the female described by Ijima and Ikeda shall be 

 referred to as the Misaki specimen). 



In the first place, the body is somewhat laterally compressed, not 

 nearly dorso-ventrally as in the Misaki specimen. The gelatinous coating 

 is much thinner than in that specimen, measuring at most 6 mm., instead of 

 20 mm., in thickness at the posterior body-end. The umbrella is equally 

 developed all around : unlike the Misaki specimen, the part of it between 

 the ventral arms is as broadly developed as at any other interbrachial space. 



In spite of the fact that the arms, except the left second and the hecto- 



1) Chall. Rep. XVI, pp. 67-68; pi. ix, figs. 7-9. 



2) Armor.. Zool. Jap., IV, rgo2, pp. 87-101; pi. ii; 3 text-figs. 



