432 PROCEEDINGS: BOSTn.X SOCIETY NATURAL HISTORY. 



very wide velum, figure G, is pushed out to form eight hemispherical 

 pouches, four of them radial and four interradial, in the planes of 

 the eight tentacles. They project so much that they are prominent 

 in profile view, as shown in figure H. May they not be homologous 

 with the pouches that become converted into marginal vesicles in the 

 vesiculated medusae ? 



"The adult medusa is shown in figs. /, J and K. When it is swim- 

 ming up from the bottom the tentacles are carried tightly curled up 

 close to the edge of the bell. When it reaches the surface they are 

 suddenly extended on all sides, shown in fig. K. They are nearly 

 straight, but their tips are a little bent and sometimes coiled. This 

 attitude is preserved only for a few seconds and the medusa at once 

 begins to sink towards the bottom, while the tentacles coil up at their 

 tips and assume the position shown in fig. I. The bell also becomes 

 flattened and nearly hemispherical, and before the animal reaches 

 the bottom of the aquarium it usually assumes the appearance which 

 is shown in fig. J. As it nears the bottom it suddenly draws in its tenta- 

 cles and rises to the surface, and again extends them, as shown in fig. 

 K. . . . The figures of the adult medusae, I, J, K, are much less magni- 

 fied than the others, which are all drawn to the same scale." 



The memoir of 1886 also contains an account, (p. 391), of a planula 

 that was reared from the egg of Turritopsis, and of the larval or first 

 hydranth which arises from the planula and forms the basis of a new 

 hydroid cormus. These stages are shown in figures 2 and 3 of plate 

 42. A record is also made (p. 391) of the fact that the planula does 

 not become converted into a hydranth, but becomes a root, from 

 which the first hydranth is formed as a bud. 



Dr. S. Rittenhouse has recently reared a number of planulae of 

 Turritopsis from the egg, and he has verified the observation that the 

 planula becomes a root, from which the first hydranth arises as a bud, 

 and he has traced the further development of the hydranth. When 

 joined to the memoir of 1886, his observations, which are contained 

 in Part 3 of this paper, give us all the prominent facts in the life his- 

 tory of Turritopsis. 



