44 THE VOYAGE OF H.M.S. CHALLENGER. 



Doliolum Tarum, Grobben. 



Doliolum krohni, n. sp. 

 These may be divided into two sections : — (l) "With numerous stigmata extending 

 along the greater part of the lengtli of the branchial sac, including the first six species ; 

 and (2) with only a few stigmata at the posterior end of the lirauchial sac, including 

 the remaining three species. 



Doliolum denticulatum, Quoy and Gaimard. 



Doliolum denticulatum, Quoy and Gaimard, Voyage de I'Astrolabe, Zoologie, torn. iii. part 2, p. 599, 



1835. 

 Doliolum denticulatum, Q. and G., Huxley, Phil. Trans. 1851, part ii. p. 595. 

 Not Doliolum denticidatum, Q. and G., Krohn, Arch. f. Naturgesch., 1852, p. 57. 

 Not Doliolum denticulatum, Q. and G., Keferstein and Ehlers, Zoologische Beitriige, p. 65, 1861. 

 Not Doliolum denticulatum, Q. and G., Grobben, Arb. zool. Inst. Wien, Bd. iv. p. 55, 1882. 

 Not Doliolum denticulatum, Q. and G., Herdman, Trans. Koy. Soc. Edin., vol. xxxii. part i. p. 93, 1883. 



This species, the oldest member of the genus, was found in 1827 on the surface of 

 the Pacific Ocean, near the islands of Yanikoro and Amboiua, by the French naturalists 

 Quoy and Gaimard, during the voyage of the " Astrolabe." They described and figured 

 it in the official account of the expedition published in 1835. The diagnosis given is 

 as follows : — 



" Doliolum, corpore minimo, hyalino, cyliudrico-ovato subtruncato, in utroque apice 

 perforate, antice crenulato ; circulis octonis salientibus." 



The short description which follows the diagnosis adds nothing of importance, but 

 merely shows that the observers mistook the branchial sac for a pair of plume-like 

 internal gills, the muscle bands for vessels, and the endostyle for an aorta. The figures ^ 

 show two views of the entire animal, a representation of the (svijaposed) plume-like gills, 

 and an end view of the anterior extremity. There appear from the figures to have 

 been ten branchial lobes, if Quoy and Gaimard are correct in designating the end 

 which they figure with denticulations as the anterior. The position of the endostyle 

 in relation to the muscle bands would rather lead to the oj)posite conclusion, but 

 probably it is represented too far back in the body. The second species of Doliolum 

 described by Quoy and Gaimard, Doliolum caudatum, is an asexual form with nine 

 muscle bands and a well-marked dorsal outgrowth. Possibly it is the Blastozooid 

 belonging to the present species. 



During the voyage of H.M.S. " Eattlesnake " in 1849, Huxley found specimens of 

 Doliolum in the South Pacific, a little to the northward of Sydney, N.S.W., between 

 Sydney and New Zealand, and in consideralile numbers just at the entrance of the Bay 

 of Islands. These he identified with the species Doliolum denticidatum described by 

 Quoy and Gaimard, and he published a detailed anatomical account with figures in the 



1 Atlas, MoUusques, pi. 89, figs. 25-28. 



