626 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
As respects the corpuscular elements of the peritoneal fluid, the Terehellce are more 
remarkably characterized than any of the preceding species of the Annelida. In the 
two species, most familiar to us on the coast of Swansea, the chylaqueous fluid is 
very large in amount. It is a thick, milky liquid, containing large compressed oval 
cell-capsules, almost individually visible to the naked eye. These corpuscles are not 
nucleated cells, but flattened vesicles filled with oil-molecules and granules. The 
cell-capsule is attenuated. Others of these large cells seem to consist only 
of lesser cells aggregated together into circular groups. Interspersed between these 
bodies may be seen another variety very different from the former. They are chiefly 
seen in the hollow axes of the tentacles moving to and fro, and in figure uniformly 
spindle-shaped, destitute of visible contents and pellucid (fig. 20). Those of Terehella 
conchilegia (Plate XXXII. fig. 21) are about one-half the size of those of this fluid 
in Ter'ebella nebulosa (fig. 20). In all other microscopic characters the latter are 
exactly like the former. 
The respiratory process in the Terebellae is divided in an equal proportion between 
the chylaqueous fluid and the blood-proper. Each tentacle is traversed by a blood- 
vessel and by a current of chylaqueous fluid. The visceral cavity of the Terebellae 
at the reproductive season is filled with ova and sperm cells. In this genus the mass 
of the chylaqueous fluid is an important agent in locomotion. 
The structure of the common earth-worm is distinguished in several material 
respects from that of those Annelids forming the subject of the preceding remarks. 
In Lumbricus the segmental partitions are complete and well-marked, tying, at very 
frequent intervals and intimately, the intestine to the integument, and consequently 
limiting, almost obliterating the peritoneal cavity. This cavity however does exist, 
and contains a viscid colourless fluid, bearing spherical, nucleated and granular 
cells (fig. 22), intermingled with pellucid cellules, which appear only to represent 
the immature phase of the former. These corpuscles seem to me to be the bodies 
which Mr. Wharton Jones has mistaken for those supposed to exist in the blood- 
proper*. The fluid of the peritoneal cavity is of almost momentary importance to life 
in the Earth-worm. Kept in a perfectly dry atmosphere even for an hour it dies. 
It cannot be revived ; and is covered by a slimy fluid which appears as if it were 
that of the peritoneal cavity exuded. In the adult state in this worm the system of 
the blood-proper is highly developed ; a circumstance which explains the diminished 
proportion of the chylaqueous fluid. That the basis of this latter fluid consists of 
water, I infer from the immediate importance of moisture to life. The fact of its 
existence, and next that of its physiological importance, are quite proved by the 
results of observation on the young Earth-worm (fig. 23). In the early stage of 
development the peritoneal fluid in this worm is, relatively, considerable in quantity. 
In the infancy of this Annelid it fulfils those functions which during adult life are 
discharged by the true-blood. The peritoneal fluid in the young abounds in spindle- 
* Philosophical Transactions, Part II. 1846. 
