CHYLAQUEOUS FLUID OF INVERTEBRATE ANLMALS. 
621 
Nemertina and Planarise, whose organization, as already stated, is remarkably ana- 
logous to that of the Cestoid Entozoa, are universally eovered externally by a ciliated 
epidermis. 
The characters of the chylaqueous fluid in the entozoon of the Hake are illus- 
trated in fig. 13. It is a thick tenacious fluid, bearing a vast multitude of 
minute, highly refractive molecules, distributed through a hyaline semifluid substance 
resembling the white of egg. I have proved, by repeated observations, that this fluid 
is the normal contents of the alimentary organ of these worms. It intimately resem- 
bles the semifluid substance which fills the blind diverticula of the digestive system 
of the Planariae. It is in both instances undoubtedly a vital, nutritive fluid. It is in 
this fluid that is performed the part which devolves upon the corpuscular elements. 
When, accordingly, in some of these sterelminthous species a space does exist be- 
tween the exterior of the digestive organ and the solid parietes of the body, that 
space is filled only with a limpid, non-corpuscular liquid, which is fitted to answer 
no other than the mechanical purpose of facilitating the slight movements of which 
the intestine is capable. It may be accepted as a rule applicable to all Entozoa and 
all Annelida, that when the intestine is intimately tied to the integuments, the ordi- 
nary chylaqueous fluid is materially reduced in volume, or altogether disappears. 
Under such circumstances, in the solid Entozoa it reappears under a new character, 
although virtually the same fluid, in the interior of the digestive system. In some 
species of Annelida, however, as the Earth-worm and the Leech, the diminution or 
suppression of the chylaqueous fluid is eompensated by a correspondingly greater 
development of the true-blood system. Future researches will inevitably show that in 
the Entozoa the blood-proper system is a very subordinate element of the organism. 
For the maintenance of the living solids, so striking in these animals is the ‘‘sim- 
plicity” of their structure, the chylaqueous fluid will be found physiologically suffi- 
cient. An attentive study of the fluids will result in the discovery of an unfailing 
clue whereby in these animals to reeoncile with physiological principles the paradox 
of the arrangement and histology of the solids. By no other road can this desirable 
point be attained*. 
* I have recently studied with great attention the valuable contributions of M. Siebold* and M. Van Be- 
NEDEN® to helminthology. I am persuaded that these distinguished men have not yet discovered the path 
which is destined to conduct the physiologist to a true understanding of the organization of the Entozoa. I 
warrant this bold statement by the facts which already my own labours have enabled me to establish. The 
fluids will unerringly conduct the future student to a perfect comprehension of the solids. The solid elements of 
these paradoxical organisms will ever remain insoluble enigmas if studied independently of, and without refer- 
' M^moire sur la Gdndration Altemante des Cestoides, suivi d’une Revision du genre Tetrarhynchus. Par 
C. T. de SiEBOLD. Traduit de I’Allemand par M. Camille Dareste, Ann. des Sciences Nat., 1851, 3™ Serie. 
^ Les Vers Cesto'ides ou Acotyles, consideres sous le Rapport de leur Classification, de leur Anatomic et de 
leur Developpement. Par P. J. Van Beneden. Bruxelles 1850, avec 26 Planches. 
4 L 2 
