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XXIV. The Development of Renilla. 
By Edmund B. Wilson, Ph.D., Fellow of Johns Hopkins University. 
Communicated by Professor Huxley, F.P.S. 
Received October 5,—Read December 14, 1882. 
[Plates 52-67.] 
The observations recorded in the following pages were made in the course of three 
summers’ work at the marine laboratory of the Johns Hopkins University, organised 
and directed by Professor W. K. Brooks, and located for the past three years at 
Beaufort, N.C., where the material for this paper was collected. 
The abundance of Renilla reniformis (Cuv.), at Beaufort, suggested the desirability 
of a careful study of its embryology, and this was rendered still more apparent by the 
studies which Mr. Mitsukuri had made upon the anatomy of the adult organism. 
I was therefore much pleased when a lucky accident, during the summer of 1880, 
put me in possession of a few very young colonies. Subsequent search over the 
ground resulted in the discovery of a considerable number of young colonies in various 
stages of growth, and I was thus enabled to make a rather full study of the growth of 
the colony from the simple primary or axial polyp up to the adult organism with its 
secondary polyps in a state of full sexual maturity. A single specimen, finally, of the 
ciliated larva was taken at the surface and kept in the aquarium until the free-swim¬ 
ming life was abandoned and the characteristic tentacles and spicules made their 
appearance. 
An outline of the general results of these observations was published in the 
American Journal of Science for December, 1880, a full description being however 
deferred in the hope of procuring still earlier stages for a study of the embryonic 
development. This hope was happily realised in the following summer, when two or 
three lots of fertilised eggs were obtained; and, finally, in the season of 1882, the 
eggs were procured in considerable abundance, and a very satisfactory study of the 
phenomena of development was effected. 
During the latter season the eggs of a Gorgonian, Leptogorgia virgulata (Edw. and 
Haime), were procured—though in small numbers only—and I have studied to some 
extent the development of this polyp also. The material was however scanty, and the 
development, so far as observed, closely similar to that of Renilla; hence these obser- 
