122 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
during the summer months. The size of the full grown 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 zoólogists 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 L-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 Aiquoride. 
Eucope shares with the Oceanidæ the limited number of marginal 
tentacles connected with sense organs. Pendant leaf-like expansions of 
the genital organs recall those of Melicertide. 
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 Berenicide, a family allied to the /Equo- 
ride ; the forking 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 Æquoridæ. 
The serration of the radial canals is a generic character of Saphenia 
and allied genera. 
The branching or sending off spurs from the radial canals of Eucope 
is a structural feature found in Gonionemus, Ptychogena, Polyorchis, 
and allied forms. The lateral offshoots in Polyorchis being, hawever, 
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. 
