398 W. K. BROOKS ON THE LIFE-HISTORY 



limpida in so many respects that I am inclined to regard it as the young of that species. 

 It is shown in PL 39, figs. 4, 5 and 6. It has a flattened, emarginated bell, simple lip? and 

 short tentacles without bulbs, and with accessory spiral tentacles. Specimens were also 

 found at the same stage of growth in Aug., 1879 and Aug., 1880. 



The Embryology and Metamorphosis of the Eutimid^e. 



In 1881 Clans called attention to the fact that almost nothing is known regarding the 

 life-history of Eutima or any of its nearest allies, and that the only observations upon 

 the development of any of the Gerynopsida^ are those of A. Agassiz (2, p. 115, figs. 

 171 and 172) who has reared the planula of Tima formosa from the egg and has given 

 a very brief description and a single figure of the hydra, although he did not observe 

 the production of medusa-buds and says nothing about the very young stages of the 

 medusa. 



Except for Claus' paper, which will be noticed presently, the only addition to our 

 knowledge of the subject is a very brief account by Merejkowsky (50) of the young 

 embryo of Irene. In the spring of 1880, Claus (GG) found a number of small hydroid 

 communities in an aquarium, in which specimens of Octorcliis Gegenbauri, Irene pel- 

 luclda and JEquora Forshalia had been placed some time before. From these hydroids 

 he obtained a number of young medusae, which, however, he did not succeed in rearing; 

 but, as he was able to collect in the open water series of young medusae of each of the 

 three species, he showed that those which he obtained from the hydroid were essentially 

 different from young specimens of Irene and ^Equora, while they were sufficiently like 

 the youngest specimens of Octorcliis which he obtained in the open ocean, to render it 

 very probable that the hydroid belongs to this species, although the gap between the two 

 is sufficiently great to render further information desirable. In the absence of any ob- 

 servations which connect the hydroid with its parent or the medusa-buds with adult 

 medusae, it is possible that the hydroid may not have been reared from the eggs of any 

 one of the three species which were placed in the aquarium, as eggs or planulae may 

 have been introduced with the water. Claus' observations render it very probable that 

 the hydroid is the larva of Octorcliis, but they do not prove it beyond question, and I 

 have been able to complete the story by actually rearing from the eggs of our Eutima 

 mira, under constant observation, a hydroid which is so similar to the one which Claus 

 figures, as to show beyond doubt that his conclusion is correct. Octorcliis is a Eu- 

 tima according to McCrady's definition of the genus, and the species which I studied is 

 very closely related to the one which Claus observed. As I have observed the seg- 

 mentation of the egg, the swimming life of the planula, its attachment and the origin of 

 the hydroid, while Claus has described the medusa-buds and the metamorphosis of the 

 medusa, the two accounts give a very complete life-history of the Eutiniidae. 



The fertilized eggs of Eutima may be obtained by placing- a few mature specimens in 

 a small aquarium or a shallow dish of sea water. They usually lay their eggs the first 

 night after they are captured, and if the species is very abundant, the water will often 

 contain enough spermatozoa to fertilize them, even when only one specimen is used; but 

 the result is much more certain if several specimens are placed in the same dish, for 



