;j(32 W. K. BROOKS ON THE LIFE-HISTORY 



ures this specimen in his PI. 12, fig. 4, and this figure is copied as fig. 3 of PI. 44, of 

 this paper. The figures of the adult which are here given, PI. 44, fig.s. 4 and 5, are 

 the only ones which have ever been published. Adult specimens are quite common at 

 Beaufort during September and October, but I have found very few during the last 

 weeks of August, or earlier, nor do the specimens of Turritopsis which are captured 

 early in August contain the larvae, although these are present in about one-third of the 

 specimens which are captured after the Cuninas make their appearance. 



By actually rearing the larva' and medusa-, I have verified McCrady's conjecture that 

 the parasitic form found in the bell of Turritopsis is the young of this species; and 

 while there was no reason to doubt this conclusion, the extremely great interest of the 

 subject, and the very perplexing character of most of our information regarding the 

 parasitic Cuninas, rendered this direct proof very desirable. 



One other species of Cunina, C. discoides, Fewkes (21), is a very rare visitor at 

 Beaufort, and I have found only a single immature specimen, which was captured out- 

 side the bar on Sept. 2, 1882. 



The Life-Histoky of Cunocantiia octoxakia. 



The J^arcomcdusaa are unquestionably the most primitive of the IIydromedusa\ and 

 we might therefore expect their ontogenetic development to throw light upon the more 

 complicated life-histories of the other members of the group, and I shall try to show 

 that this actually is the case, and that the series of species which have been carefully 

 studied does present us with the successive steps through which metamorphosis has 

 become converted into metagenesis or alternation of generations. Our species furnishes 

 one very important link in this chain, and as I have been able to verify all the points in 

 McCrady's classic, but almost inaccessible paper, and to add many new ones, I shall 

 give as complete an account as possible of the metamorphosis, using my own material 

 as well as McCrady's description. 



The life-history is illustrated by Plates 13 and 44. Figs. 2 and 5 of PL 43, and figs. 3 

 and G of PI. 44, are copied from McCrady, while the others are original drawings from 

 nature. 



McCrady gives (49, p. 10) the following account of the discovery of the larvae. "In 

 the early part of July, I found the first full-grown specimens of Turritopsis. Among 

 them was one somewhat larger, perhaps, than the rest, which I took with the bell in- 

 verted. When placed under the microscope, conceive my astonishment to find, clinging 

 to the bell and sides of the proboscis, numerous little animals of singular aspect, each 

 of which appeared to be sustaining his hold by a four-legged pedestal, and to be writh- 

 ing about in the water a long appendage, the meaning of which I could not understand. 



* * * It was not until the 15th of August, that I again encountered the same 

 phenomenon, in a smaller size of Turritopsis, of which quite a number were taken. 

 I found the cavity of the bell around the proboscis again occupied by these larvae" (see 

 PI. 44, fig. 6, which is copied from McCrady's PL 5, fig. 28), "but besides these formerly 

 observed, were others, which were gradually becoming Medusa?, and still others which 

 had assumed the Medusa-form already, and, lastly, to complete my satisfaction, I saw 

 them, after expulsion from their former abode, swimming about freely in the water, 



