§$ 188, 189. THE ACEPHALA. 203 
CHAPTER V. 
DIGESTIVE APPARATUS. 
§ 188. 
The digestive canal of the Acephala is formed, throughout the class,upon 
a single plan. It always consists of irregular convolutions which are sepa- 
rated with difficulty, for their walls are generally not covered by a peritoneal 
envelope, but are intimately blended with contiguous organs and especially 
the liver and genital gland. The oral and anal openings, which are always 
present, are not upon the surface of the body, but are situated in a cavity 
circumscribed by the mantle.® 
The mouth has always tumid lips and often tentacular appendages. Its 
cavity has neither distinct muscular walls, nor any trace of a masticatory 
apparatus. It passes either directly, or by a short cesophagus, into a kind 
of stomach which gradually contracts into a longer or shorter intestine, 
scarcely different from it in its intimate structure. The extremity of the 
intestine often projects into the cavity of the body, as a kind of papilla, 
upon the end of which the anus is situated. Internally, this canal is lined 
throughout with a very distinct, ciliated epithelium. 
The food of these animals, which consists of slime and small organized 
bodies, is taken into the cavity of the body with the water, and is conduct- 
ed to the mouth by the ciliated epithelium which lines this last. In a sim- 
ilar manner the faeces are rejected with the refuse water. 
§ 189. 
The very feebly-developed digestive canal of Salpa consists only of a 
small knob (Nucleus) situated in the posterior part of the cavity of the 
body. It connects with a furrow formed by two narrow folds situated 
along the ventral median line. ; 
This furrow may become a canal by the joining of its borders, and its 
posterior extremity, which is a little lateral, opens directly at the entrance 
of the intestinal canal which is surrounded with a lip, and ought therefore 
to be regarded as a mouth. The folds of this furrow arise directly behind 
the anterior respiratory orifice, and are very probably covered with cilia, 
by which, solid particles of food taken into the body during respiration, are 
borne towards the mouth.” 
1 With many Acephala, as with the Ascidiae and 
Salpinae whose mantle is entirely closed with the 
exception of the two respiratory orifices, it is only 
in an improper manner that the terms oral and 
anal can be given to these orifices. 
1 With Salpa cordiformis, and maxima, I have 
seen this furrow quite distinctly. It appears to be 
present in all species. Cuvier has already men- 
tioned and figured it (Mém. sur les Thalides, &c., 
p. 12, fig. 1, 2, 3, &c., y.), and it has also been no- 
ticed by Savigny (Mém. &. p. 124, Pl. XIV. fig. 
1, 2, 1.), and Eschricht (Over Salperne, p. 26, 
fig. 4, 8, 18, m.); but they describe it as a dor- 
sa] furrow and a dorsal fold, for they have taken 
the abdominal cavity of these animals for the back. 
That of Salpa gibbosa is quite distinctly figured in 
the Catalogue of the Physiological Series, &., I. 
Pl. VIL. fig. 1,k. This furrow corresponds, prob- 
ably, less to an open cesophagus, than to the ten- 
tacle-furrow which, with all the Lamellibranch- 
ia, is situated upon the two sides of the mouth. 
