M. Ussow’s Zoologico-Embryological Investigations. 331 
subsidiary organs belonging to the sanguiferous system I 
reckon:—a, the “‘ band-like organs”’ (streifenférmige Organe*), 
most frequently to be met with in Salpa pinnata; and d, the 
paired, spherical bodies (“ ovatre,” Sav.) of the Pyrosomata, 
which lie in the inner mantle, between the ganglion and the 
endostyle, on both sides of the body. These organs originate, 
I believe, from a thickening of many united blood-vessels. 
They consist of thin epithelial walls; and their cavity is always 
occupied by free bluish corpuscles, very like the blood-spherules 
of the Tunicata, and the protoplasm of which is very contractile. 
In the embryos of Salpa pinnata, the “ band-like organs ” 
appear very late, at first as undefined aggregates of contractile 
bodies, which afterwards become converted into elongated 
cylindrical, ‘‘ band-like organs.”’ ‘Their number in the nurse- 
form of Salpa pinnata is five on each side ; in the chain-Salpe 
there is only one such organ on each side. Their function 
remains unknown to me, 
V. The Digestive Organs. 
The digestive organs of the Tunicata may be divided into :— 
the true alimentary canal, which consists of a short cesophagus, 
a simple or double stomach, an intestine, and a rectum with 
the anus; and the glandular subsidiary organs—the ciliated 
arch and more or less separated masses of hepatic cells, which 
sometimes possess a proper efferent duct, opening into the 
lower part of the stomach (in some Cyclomyarie). 
The histological structure of all these digestive organs is 
very uniform. ‘They consist of:—l, 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 
by Huxley§ are simple glands (“‘pancreas” of other authors?), 
which open at the surface of the mucous membrane of the 
intestinal canal and stomach (simple Ascidia, Salpe). 
* Leuckart, Zool. Unters. Heft ii. pp. 45, 46, Taf. 1. fig. 2; Carus, Ic. 
Zoot. Taf. 18. figs. 35, 349. 
t+ Mém. sur les Anim. sans Vert. partie 2, pl. xxii. fig. 1. 
t When the “ band-like organs” are isolated and in a fresh state, these 
corpuscles push forth long pseudopodia, and move very quickly, like the 
white blood-globules of the higher animals. 
§ Phil. Trans. 1851, pp. 570 & 711, pl. xv. fig. 6. 
