F. S. CONANT ON THE CUBOMEDUS^. 23 



Discomedusan Cassiopea which was found in the same region over by 

 Port Royal. Whether or not the animal made intentional efforts to 

 escape capture could not be decided satisfactorily, but certain it was that 

 they did escape often enough by swimming quickly below the surface of 

 the semi-opaque water. 



Tripedalia endured captivity much more hardily than the Charybdea, 

 and would live in aquaria happily enough for a number of days no 

 attempt was made to see how long. Specimens with their stomach 

 pockets filled with ripe spermatozoa, or with young at any stage from 

 egg to planula, were taken in plenty from the latter part of June to the 

 latter part of July. In each female the young were all at the same 

 stage. The embryos were thrown out in the aquaria as free-swimming 

 planula', which settled down on the bottom and sides of the glass in a 

 day or two, and quickly developed into small hydras with mouth and 

 typically with four tentacles (and four taenioles, W. K. B.), though three 

 and five were by no means uncommon. In this condition they lived for 

 three weeks without essential change, and they were still giving no 

 promise of further development when the laboratory broke up and the 

 jars had to be emptied. 



b. External Anatomy. 



The structure of the Cubomedusae seems to be that of a type well 

 established, and accordingly offers no very wide range of diversity among 

 the different genera. The Charybdea that has just been described is a 

 very typical form and will serve well as a standard with which to com- 

 pare our species of Tripedalia. The resemblances are so close that a 

 detailed account of the anatomy of the second form would involve much 

 needless repetition. It is hardly necessary to do more than merely point 

 out in what points Tripedalia resembles Carybdea and in what points it 

 differs. 



The form of the bell is less pyramidal than in Charybdea. Some 

 measurements even gave the breadth greater than the height. The 

 external surface is divided, as typical for the Cubomedusae, into the four 

 perradial sides and the four convex interradial ridges, and the furrows 

 that separate these areas are with one small exception exactly the same 

 as those of Charybdea, as may be seen by comparing the series of 

 sections of Tripedalia (Figs. 21-30) with those of Charybdea (Figs. 6-15). 

 The exception is almost too slight to mention. The ad radial furrow in 

 each octant which sets off the corner rib from the perradial surface in 



