CHYLAQUEOUS FLUID OF Ix\ VERTEBRATE ANIMALS. 
615 
The Asteriadee in general coincide with Asterias rubens in the microscopic and 
chemical characters of the chylaqueous fluid. In Solaster papposa (hg. 9), the 
motion of this fluid in the hollow interior of the membranous appendages may be 
readily demonstrated in a living specimen. The morphotic elements of the fluid in 
this genus consist of nucleated cells, flattened in form, charged in general with 
little or no granular matter, inferior in dimensions to those of Asterias. The mole- 
cular base, as obtained by evaporation, is small in amount, while the fluid evidently 
holds albumen in solution ; for when collected in sufficient quantity, and treated 
with nitric acid, it becomes distinctly opalescent. In fig. 9 these corpuscles are 
accurately represented as they were found in several specimens examined, and mag- 
nified 350 diameters. They vary so much among themselves, and according to the 
size of the specimen, that exact measurements of individual examples would yield 
no useful results. In Cribella oculata (fig. 10) the cells of the chylaqueous fluid 
are more globular in figure; the largest are distended with secondary cellules, and 
nucleated, the involucrurn of the maternal cell being more distinct than ordinary in 
other genera. In this species also, the granular matter of the fluid is wanting; nitric 
acid, however, gives an obvious opacity. 
In the Echimdce the blood presents a slightly higher grade of development than that 
of the Asteriadse, and the digestive canal is furnished with a second orifice. The canal 
is always found to be filled with solid ingesta, composed for the most part of sand 
and clay. These characters constitute important zoological features. They explain 
the fact of the diminished bulk and pure water-like appearance of the cotjtents of 
the peritoneal cavity in Echinus. I have proved, as conclusively as a negative pro- 
peritoneal space ; there are therefore no open perforations in the parietes of the digestive caeca. From the 
interior of the latter organs into the former space, no fluids therefore can pass hut by exosmosis. When a 
fresh, living Asterias is immersed in fresh sea-water, coloured with cochineal or carmine, and allowed to 
remain thus immersed for about an hour, and then carefully washed in clear sea- water, and then opened, it will 
be found that the contents of the peritoneal cavity are perfectly free from the smallest trace of the coloured 
fluid, while it may be always, under the conditions of this experiment, detected in the interior of the cmca. 
These and parallel observations prove that Asterias continually, and for the purpose of feeding, draws into the 
stomach a large volume of water, sending by a determinately directed pressure, a portion into the caeca, and 
rejecting the remainder again by the mouth. Of hundreds of living, healthy Starfishes which I have dissected, 
it is remarkable to relate, that not one has ever contained anything whatever in the stomach. The primary 
process of digestion is performed in the Asteriadae in the central stomach, and that rapidly, the unappropriated por- 
tions being immediately disgorged, while the rest is admitted into the digestive cseca. The caeca are never charged 
with anything but sea-water, rendered slightly opake by the chyme and the parietal secretions of these parts. 
This fluid therefore exhibits a grade of organization inferior to that contained in the peritoneal cavity, since the 
latter is replete with unquestionably organized elements, of which the former is destitute. The true food of 
the Starfish appears therefore to consist of nothing but sea- water, and those albuminized organic substances 
which it may perchance hold suspended or dissolved. According to my examination, the chylo-peritoneal fluid 
in all the asteroidal and globular Echinoderms is intimately analogous in composition. In the Vermigrade 
orders, it resembles much more that which exists in the Annelida ; it is beyond question here a vital fluid. 
In the intestine of the Holothuriadse and Sipunculidse, sand and other refuse matter are always found. 
