620 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
zoological series*. Excluding for the present the cystic orders, the two leading divi- 
sions, established by Professor Owen under the appellations of Coelel- and Sterelmintha, 
are distinguished from each other by a deep line of demarcation, two great classes of 
Entozoa which differ in organization far more remarkably than any helminthologist 
has ever yet supposed. On this occasion, however, it is proper that my observations 
should be confined to a consideration of the fluids. 
In the Nematoidea the intestine is scarcely at all attached to the integumentary 
cylinder. The space which intervenes is filled with a corpusculated fluid, remarkable 
for its viscidity and the molecule-like size of its corpuscles, which is truly chyl- 
aqueous. The system of the blood-proper in all Entozoa is very inferiorly deve- 
loped, and the blood-proper itself in all species is colourless and perfectly fluid, 
holding no globules or cells of any sort in suspension. In this particular they are 
identical with the Annelida. This fluid, contained in the peritoneal cavity, is the 
real reservoir of their nutrition. Traced through the class in living specimens, 
its history will prove the history of the real mechanism of nutrition in these animals. 
The Cestoid Entozoa differ from the Trematoid and Nematoid orders, in the same 
characters exactly, as the Nemertine Annelida differ from all the other orders of 
their class. In the Cestoidea the alimentary canal is intimately adherent to the inte- 
guments, obliterating the peritoneal space and constituting the solid-worms (Sterel- 
mintha) of Professor Owen. The true chylaqueous fluid is contained in the canal 
in this order, a disposition of the fluids which will be found to prevail also in many 
species of Trematoid and Nematoid worms. Differing in anatomical situation, these 
two varieties of fluids will be found to differ in physical characters. 
In those Entozoa in which the chylaqueous fluid is contained in the recesses of the 
alimentary organ or digestive canal, it presents characters which distinguish it con- 
spicuously from that of those families in which it occupies the cavity (visceral) with- 
out the alimentary canal. In the latter case it oscillates freely in the cavity, driven 
by the muscular contractions of the intestinal and integumentary parietes. In the 
former it moves very little in its containing cavity. This is true of all Entozoa allied 
to Tcenia. The fluid contents of the alimentary system, wdiich in many species had 
neither an inlet nor an outlet, is quite stationary. In these worms no part either of 
the exterior or interior of the body is ciliated, although those Annelida, such as the 
* This observation is founded upon, and justified by, the results of my researches into the organization of 
some of the Nematoid and Cestoid Entozoa', but especially into the anatomy of the Nemertine Annelida, under 
which division I include the Gordiusidcd, Planariadce, Borlasiadce and Liniadcs orders of Annelids, on the true 
structure of which no light has hitherto been thrown by anatomists, and between which and the Cestoid En- 
tozoa especially, affinities, in structural plan of a remarkable character, and hitherto unrecognised, exist. As 
my opportunities for examining recent Entozoa have been few, I regret that I cannot in the text present many 
examples of the exact microscopic characters in this class of the fluids. 
' See the author’s Report on the British Annelida, Transactions of the British Association, 1S51. 
