CHYLAQUEOUS FLUID OF INVERTEBRATE ANIMALS. 
603 
every species, the seat and scene of the processes of digestion, sanguification and 
respiration ; it is, in addition, the direct agent of nutrition. It is chyme, chyle and 
blood in itself. In the zoophyte it is the only fluid element of the organism. In the 
tentacles of Tubularia indivisa, the fluid of the visceral cavity can be distinctly seen 
in motion in the axial channel. The fluid is charged, in this species, with minute 
albuminous granules, irregularly grouped, and formless or unorganized, appearing to 
consist simply of solid spherules, resulting from the solidification of albumen, Plate 
XXXII. fig. 1. 
The bulk of this fluid consists of salt water ; for when the specimen dries and the 
fluid evaporates, cubic crystals of chloride of sodium are seen amidst the albuminous 
molecules. This fluid was first seen in motion by Lister, then by Milne -Edwards, 
and by Van Beneden. It may be well here to observe, that the molluscan polypes of 
the Flustrce, Escharce and Bowerbankia, are ciliobrachiate, and that the digestive 
organs are divided from the visceral cavity. In.these genera, therefore, the fluid con- 
tents of this cavity receive no direct admixture of salt water through the tentacles, for 
the extremities of these organs are not perforate. It is replenished only through the 
stomach ; tlie water is submitted to the agency of this organ before it enters into the 
visceral chamber. This fact explains the circumstance, that in these molluscoid 
polypes the fluid of the visceral cavity, as compared with that of the former group, 
presents a higher organic composition ; its cells are corpusculated and evidently 
organized ; many bear globules of oleine, although comprising several individual 
forms of cell ; they are constant in their microscopic characters in the same species. 
The fluid is aerated in the tentacles. It is true-blood in its composition and func- 
tions, fig. 2.*. 
Medusas. — In all Acalephse the digestive cavity is prolonged into a system of canals 
into which the contents of the stomach pass by direct communication. The gastro- 
vascular channels are to the Acaleph what the visceral cavity or the hollow interior 
of the polypidom is to the Polype. In both cases the contained fluid consists of a 
chylaqueous compound. In both, the containing chambers and canals are lined by 
a vibratile epithelium'!'. 
* I have recently succeeded in bringing under direct demonstration the movements of the fluid in the peri- 
gastric cavity of the little freshwater Hydra. The distal ends of the tentacles are imperforate. The fluid is 
charged with minute oleous molecules. This marvellous little being is no longer an organic paradox. Its 
fluids and solids are now intelligible ; the essential elements of its organism are unravelled. 
t I had repeatedly and beyond doubt established this fact (by numerous observations on several species of 
Pulmograde and Cirrhigrade Medusae found in the Bay of Swansea and the Bristol Channel) long before the 
advantage occurred to me of perusing the valuable paper of Mr. Huxley in the Philosophical Transactions ‘ On 
the Anatomy and Afl5nities of the Family of the Medusae,’ Part II. 1849. With reference to the digestive 
cavity of the Cryptocarp and Phanerocarp families Mr. Huxley remarks, “ Whatever its appearance, it will 
always be found to be composed of two membranes, an inner and an outer. These differ but little in structure ; 
both are cellular, but the inner is in general softer, less transparent and more richly ciliated.” In the same 
paper a similar observation occurs in relation to the IlhizostoraidEe, but from his memoir I cannot discover that 
mdccclii. 4 I 
