REPORT ON THE TUNICATA. 



17 



admirable piece of work, — especially when we remember that the only available 

 material was a single colony preserved in spirit, from which sections were cut and 

 mounted in glycerine. 



In 1861 Keferstein and Ehlers' gave an account of the anatomy of specimens of 

 Pyrosovia giganteum and Pyrosoma elegans obtained at Naples and Messina. Their 

 work was carried on about the same time as that of Huxley, and forms an independent 

 corroboration of his results. The work of the German authors deals mainly, however, 

 with the anatomy and histology ; they only touch briefly upon the embryology and the 

 gemmation. 



The only remaining work that need be noticed is Kowalevsky's ^ memoir on the 

 development of Pyrosoma, which appeared in 1875. This celebrated embryologist 

 gave an elaborate account of the life-history of Pyrosoma, confirming Huxley's 

 discoveries, but tracing the stages more minutely, and going into further histological 

 detail. No jiapers of importance have been published since then, and no new species 

 of Pyrosoma have been described. 



The genus, then, contains so far only the three species known to Lesueur in 1815, 

 viz. : — 



Pyrosoma atlanticum, Peron. 

 Pyrosoma elegans, Lesueur. 

 Pyrosoma giganteum, Lesueur. 



To these the Challenger investigations have added a new species of gigantic size 

 obtained twice in the Atlantic. It 

 will be found described below under 

 the name of Pyrosoma spinosum, 

 n. sp. 



The characters of this group of 

 Ascidians, the Ascidiai Salpiformes, are 

 very well marked. The shape of the 

 colony and its free-swimming condi- 

 tion distinguish it clearly from all 

 other Tunicata. The only form which 

 approaches it in shape of colony is 

 Ccelocorraus huxlcyi,'^ and it is doubtful 

 whether that species is free-swimming, 

 or merely lies unattached at the sea- 

 bottom. 



Fig. 1. — Colony of Ptirosoma, natural size (from the Encyolopsedia 



Britannica, 9th ed.). 



A. Side view. B. End view. 



1 Zoologische Beitrage, iv., Bemerkungen Uber die Anatomie von Pyrosoma, p. 72, Leipzig, 1861. 

 ^ Ueber die Entwickelungsgeschichte der Pyrosoma, Arcliii' f. Mikr. Anat., Bd. xi. p. 597. 

 5 See this Report, Part II. 1886, p. 318. 

 (ZOOL. CHALL. EXP. — PART LXXVI. — 1888.) Gggg 3 



