M. J] mov^'' B Zoohgico-Emhryohgical Investigations. 331 



sub.sidiaiy organs boloui^ing to the .sanguiferous system I 

 reckon: — a, the "band-like organs" (streifenformige Ot'gane'^)^ 

 most trequently to be met with in Salpa pinnata ; and i, the 

 paired, spherical bodies (" ovairej^ Sav-t) of the Vyrosomata^ 

 whieli lie in the inner mantle, between the ganglion and the 

 endostylc, on both sides of the body. These organs originate, 

 I believe, from a thickening of many iniited blood-vessels. 

 They consist of thin epithelial walls ; and their cavity is always 

 occupied by free bluish corpuscles, very like the blood-spherules 

 of theTunicata,and the protoplasm of which is very contractile J. 

 In the embryos of Salpa pinnata, tlie " band-like organs " 

 appear very late, at first as undefined aggTcgates of contractile 

 bodies, which afterwards become converted into elongated 

 cylindrical, " band-like organs." Their number in the nurse- 

 form of Salpa 2)innata is five on each side ; in the (Aivan- Salpce 

 there is only one such organ on each side. Their function 

 remains unknown to me. 



V. Tlie Digestive Organs. 



The digestive organs of the Timicata may be divided into : — 

 the true alimentary canal, which consists of a short oesophagus, 

 a simple or double stomach, an intestine, and a rectum with 

 the anus ; and the glandular subsidiaiy organs — the ciliated 

 arch and more or less separated masses of hepatic cells, which 

 sometimes possess a proper eflcrent duct, opening into the 

 lower part of the stomach (in some Cyclomyarice). 



The histological stnicturc of all these digestive organs is 

 very uniform. They consist of: — 1, a more or less thin 

 serous membrane, into which looped blood-vessels {e.g. in the 

 simple Ascidia) and nerves penetrate ; 2, a one-layered inner 

 epithelial envelope, the glandular and frequently vibratile cells 

 of which are arranged upon its smooth or much-folded inner 

 surface. The absorption of the alimentary material takes 

 place directly through the thin walls of the blood-vessels. 

 The Tunicata do not possess any special lymphatic vascular 

 system. The tubes formerly designated as lymphatic vessels 

 byHuxley§ arc simple glands (^'"pancreas"''' of other authors?), 

 which open at the surface of the mucous membrane of the 

 intestinal canal and stomach (simple Ascidia, Salpcv). 



* Leuckart, Zool. Unters. Heft ii. pp. 45, 46, Taf. 1. fig. 2 : Carus, Tc. 

 Zoot, Taf. 18. figs. 3.% .S4i7. 



t Mt5m. snr les Anim. sans Vert, partie 2, pi. xxii. fig. 1. 



X 'WTien the " band-like organs " arc isolattnl and in a fi-esli .state, these 

 corpu.«icles pn.'^h forth long pseudopodia, and move veiy quickly, like the 

 white blooo-globules of the higher animals. 



§ PhU. Trans. 1851, pp. 570 & 711, pi. xv. fig. G. 



