934 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



Subfamily COLLASPID^, Haeckel, 1879. 

 Atolla, Hseckel, 1879. 



(Plates I-V.) 



The genus Atolla, one of the most extraordinary forms of deep-sea 

 medusje, is represented iu the collections made by the Albatross by 

 several specimens. It will probably be found when live specimens are 

 studied that we have in the Gulf Stream more than two species, which 

 are possibly represented in this collection. The differences which the 

 several specimens exhibit are very great, but due to the state of pres- 

 ervation rather than to structural modifications. At present they are 

 all placed in two species, to which I have given the names Bairdii and 

 Verrillii. 



The only known examples of this genus which have been described 

 are five specimens collected by H. M. S. Cliallenger* and placed in the 

 species Wyrillii by the founder of the genus. 



Hteckel unites Atolla with a like genus, CoUaspis, in a sub-family, 

 the Collasi)id{e,t of which these two genera, each with a single species, 

 are the sole members. 



The most important difference between these two genera lies in the 

 structural feature, observed by Ha;ckel, that in Collaspis the genitalia 

 are regularly distributed at equal distances from each other on a ring 

 situated between the peripheral border of the line of junction of the 

 proboscis and the inner edge of an inner coronal muscle {mus. cor. i.), 

 while in Atolla these sexual bodies are arranged in four pairs, the in- 

 tervals between the pairs being greater than that between the two 

 glands which compose a single pair. In several of the specimens which 

 are found in the collection before me and included in the genus Atolla, 

 the whole lower floor of the subumbrella was so ruptured in capture 

 that it is impossible for me to investigate the character of the genitalia 

 and their location in reference to each other. In still others, characters 

 of both genera appear on the same specimen, so that, from what I have 

 seen of the alcoholic rej^resentatives and the tendency to distortion 

 which they exhibit, I find great difficulty in separating the two genera. 

 The resemblances between the organs which were present and the same 

 in other specimens, where the ovaries have the arrangement character- 

 istic of Atolla, have led me to refer all my specimens to this genus. 



* Report on the Scientific Results of the Voyage of H. M. S. Challenger. Zoology. 

 Vol IV. No. II. Report on the Deep-sea Medusse dredged by H. M. S. Challenger, 

 by Prof. Ernst Hteckel, M. D., Ph. D. 



t Op. cit., p. iii. By an unfortunate tyi^ographical error iu his diagnosis of the Col- 

 laspidtB, Haickel excludes in this place the genus ^/o??« by assigning to the sub-fainily 

 " 1(J to 18 sense-clubs " or luarginal sense-bodies. Atolla has from (19 teste Hieckel) 

 y'2-28 sense-clubs as far as yet observed. The reading of the diagnosis in his Sys- 

 tem der Medusen is 16-32, which was probably intended to be repeated in this instance. 

 In Plate 29 (oj). cit.), Figs. 1, 2, 3, where the marginal lapjiets ought to be shown, 

 they are omitted. In Fig. 4 they are represented. 



