122 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



during the summer months. The size of the full gi'own Eucope is so 

 small that with an ordinary hand lens striking variations can at once be 

 detected, and it is possible with a low power to pass in review with 

 comparative ease a large number of specimens. 



We hope also to call the attention of zoologists to the advantages 

 of photography, not only in an investigation of this kind, but also to 

 its application for ordinary purposes of delineation. (See Plate VI. 

 Figs. 3-6.) 



Dr. Woodworth photographed the specimens reproduced here on 

 Plates I.-VI., and he has written a short account of the methods he 

 followed. 



In reviewing the variations we have observed in one species of Eucope 

 (E. diaphana), we may call attention to the similarity of these variations 

 which occur in this simple Medusa to structures found sometimes in 

 closely allied genera or families, and even in some cases to characters 

 of groups considered as only distantly related to the genus we have 

 examined. 



The great number of marginal tentacles in Eucope they have in com- 

 mon with the ^quoridae. 



Eucope shares with the Oceanidse the limited number of marginal 

 tentacles connected with sense organs. Pendant leaf-like expansions of 

 the genital organs recall those of Melicertidae. 



The presence in Eucope of spurs at the base of the marginal tenta- 

 cles recalls similar structures in Zygodactyla, Halopsis, and the like. 



The forking or branching of the radial canals below the genitals is 

 found also in Willia and in the Berenicidae, a family allied to the >iEquo- 

 ridre ; the foi-king is symmetrical in the latter, and asymmetrical in the 

 former genus. 



The increase in number of the radial canals from the pouch at the 

 base of the manubrium is a structural feature which is characteristic 

 of the ^Equoridae. 



The serration of the radial canals is a generic character of Saphenia 

 and allied genera. 



The branching or sending oflP spurs from the radial canals of Eucope 

 is a structural feature found in Gonionemus, Ptychogena, Polyorchis, 

 and allied forms. The lateral oflFshoots in Polyorchis being, however, 

 arranged in regular succession on each side of the radial canal, much 

 like the rounds of a ladder. 



The anastomosing of the radial canals is a feature now characteristic 

 of the Discophores. 



