708 
Now in studying a series of transverse sections of a Sa/pa which 
had had abundant food, we find as we approach the oesophagus a mass 
of material answering to the description of Korotneff’s ‘rhizopod’. 
It takes staining readily and may be traced backwards into and through 
the oesophagus, stomach and intestine. As the sections approach the 
rectum however, the mass gradually ceases to take staining and is 
much more distinctly marked out from the intestinal wall, having had 
all the organic matter digested out, and consisting only of the inorganic 
remains which do not take stain. » The alimentary matter of Salpae 
is composed of animal and vegetable elements in nearly equal propor- 
tions, and the microscope reveals the calcareous shells of Foramini- 
fera, the beautifully sculptured frustules of Diatomaceae, keen 
silicious needles, and the sharp armatures of minute Crustacea®.« 
In the forepart of the intestinal canal, the mass takes staining almost 
as readily as the walls of the gut itself, seeming to merge into the illy 
defined epithelium of the latter, and it is scarcely possible to say, 
where the food-bearing mucous thread ceases, and the intestinal epi- 
thelium begins, especially as this has a rugous arrangement. 
That we have here to do with a form of digestion entirely anomalous 
aud unprecedented I cannot believe and must beg leave to differ from 
Dr. Korotneff on this point. Fol and others have recognized the 
endostyle as a sort of salivary gland and have traced its food-laden 
mucous thread into the stomach of the living animal; while I have 
been able to trace the same thing in well preserved specimens. 
I have also several series of sections from animals which must 
have been without food for some time previous to death, in which the 
lumen of the intestine is not only free of food, but of any obliterating 
mass of cells, or plasmodia. The only protoplasmic bodies not food are 
certain Gregarina-like organisms adhering to the walls in various parts 
of the intestine, and which I consider to be parasites. These give on 
section the appearance of the large »scattered cells entirely free from 
their surroundings« which Korotneff figures, and regards as »ana- 
logous to the great stomach cell of Anchinia.« I shall take my first op- 
portunity to examine these structures in the living Sa/pa, but I am now 
forced to conclude that Dr. Korotneff has endowed the food-bearing 
mucous thread with a power it does not possess, and that Sa/pa do not 
exhibit any unusual form of digestion, and that there is no immediate 
cause on their account for questioning the high genetic place occupied 
by the Tunicates. 
6 J, O. Macdonald, An account of the examination of the alimentary matter 
of Salpae. Ann. Mag. Nat. Hist. 1857. XX. 
