304 W. K. BROOKS ON THE LIFE-HISTORY 



The seventeen species which are enumerated by Haeckel are arranged by him in 

 eight genera, five of which are new, and the eight genera are divided into two groups: 

 the Sapiiexii>.i:. or Eutimidse with four reproductive organs, and the Octorciiidje or 

 those with eight; but as the reproductive organs are sometimes four and sometimes eight 

 iu two of our species, we cannot regard this division as a natural one. Haeekel's genera 

 differ in the number of reproductive organs, the presence or absence of marginal cirri, 

 and the number of tentacles, but as all of these characteristics are either variable or sub- 

 ject to change during growth, it is possible that a more complete knowledge of the life- 

 histories of speeies which have been described from single specimens will compel us to 

 make a very considerable reduction in the number of genera. 



Haeekel's personal familiarity with the medusae undoubtedly exceeds that of any other 

 writer, and all students must bear testimony to the great value of the laborious researches 

 into the perplexing literature of the subject, the results of which he has given us in his 

 "System derMedusen." My own studies have taught me the value of this work, and I 

 hesitate to propose any change in Haeekel's classification ; but his arrangement of the 

 species of Eutimidas is not even available as an artificial key, for his genus Eutima is 

 characterized by the presence of only four reproductive organs and numerous marginal 

 cirri, while all my specimens of Eutima mira, a species which he places in this genus, had 

 eight reproductive organs, and while nearly all of them had marginal cirri a few had 

 none. His genus Octorchandra is characterized by eight reproductive organs and numer- 

 ous cirri ; but McCrady says that our Eutima variabilis ( Octorchandra variabilis, Haeckel) 

 sometimes has only four reproductive organs, and my specimens had no marginal cirri. 



The genus Eutima, v> originally established by McCrady, is equivalent to Haeekel's 

 family Eutimidas, and as ail i. species are very closely related to each other, while 

 several of them are as yet very imperfectly i-r ">wn, it does not seem practicable to divide 

 them into a number of genera at present. 



Genus-Diagnosis. Eucopidae with eight adradial marginal vesicles, and with the stom- 

 ach at the tip of a gelatinous peduncle from the apex of the umbrella. Reproductive 

 organs linear in the course of the four radiating tubes, which themselves extend down 

 the peduncle to the stomach. 



Remarks. The reproductive organs are often disposed in two masses on each radiat- 

 ing tube, one on the sub-umbrella and one on the peduncle, as shown in PI. 30, but 

 McCrady states that some specimens bear them only on the peduncle, some only on 

 the sub-umbrella and some in both positions, and I have found specimens of Eutima 

 mira in which ova were scattered along the whole course of the tube, from near the bell 

 margin to the base of the stomach, although as a rule they are divided into two 

 sharply defined regions separated from each other by an area where the canal bears no ova. 

 This area is often longer on one of the tubes than it is on the other, and the two ovaries 

 in one quadrant are sometimes confluent, while those in the other quadrants are distinct. 

 "We must therefore agree with McCrady that, far from furnishing a basis for a division 

 into genera, the number of reproductive organs cannot even be used to separate species; 

 that they may be double or single, and that when single they may be placed either on 

 the peduncle or on the sub-umbrella, or they may stretch over both regions without inter- 

 ruption, and that all their variations may occur in one and the same species. In the 



