REPORT ON TUE TUNICATA. 97 



The alimentary canal lies behind the liraneliial sac, and the anus opens ventrally 

 on the surface of the body in front of tlie stigmata. 



The reproductive organs arc placed at the posterior end of tlie body. 



(Tcmmation does not take place, and alternation of generations anel metamorphosis 

 <lo not occur in tlie life-history. 



This order corresj)onds to Balfour's ' group Perennichordata. It includes a single 

 I'amily, the Appendiculariidse. 



This is one of the most interesting groups of the Tuuicata, as it shows more 

 i'()m})letely than any of the rest the characters of the original ancestral forms. Its 

 nieml)ers have undergone comparatively little degeneration, and consequently they 

 correspond more nearly to the tailed-larval condition than to the adult forms of the 

 other groups of Tunicata. 



Family AprENDicuLARiiD.E. 



Body more or less ovate with the longer axis antero-posterior, and having a 



large appendage (the tail) attached to the ventral surface. The lu'anchial 



aperture is anterior. 

 TJie Test is periodically developed into a very large, investing capsule which is 



after a time cast off from the body. 

 T7ie Branc/tial Sac is simple, and has onl}^ two openings, which are placed 



one on each side of the ventral edge, and lead to separate atrial apertures. 

 TJie Nervous System consists of a large ganglionic mass placed dorsally near 



tlie anterior part of the body, and a nerve cord with ganglionic thickenings 



which is continued posteriorly into the appendage. 

 Tlie Alimentary Canal lies posterior to the branchial sac. The anus opens on 



the exterior of the body. 

 The Reproductive Organs, like the anus, are independent of the atrial apertures. 



All the members of this family are minute and free-swimming. They occur on tlic 

 surface of the sea in most parts of the world. 



The first form belonging to this family was made known by Chamisso" in 1821 

 under the name of Apx>endictdaria jlagellum; but the description and the figures 

 are so vague that it is really impossible now to say with certainty which species, or 

 even which genus, of the Appendiculariida; Chamisso found. The specimens were 

 olrtained in Bering Strait during the circumnavigating expedition under Kotzebue 

 in 1815-18. Some years afterwards von Mertens,^ voyaging in tlie same seas, found 



' Comparative Embryology, vol. ii. p. 8, Loiulon, 1881. 



2 De animalibus quibusdani e classe vermium, etc., fasc. 2, p. 363, Acad. Cms. Lcop., Nova Atla, torn. x. 1821. 

 ^ Beschreibung dcr Oikopleuia, Mem. Acad. d. Sci. SI. Peler.yh., sOr. 6, torn, i., p. 20."), 1831. 

 (ZOOI-. CHALL. EXP. — PART LX.XVI. — 1888.) Gggg 13 



