112 
DR. C. H. JONES ON THE STRUCTURE 
as the hornologue of the hepatic apparatus we have just examined, I will enter on a 
rather more particular account of it, which will disclose I think some characters 
illustrative of hepatic structure in general. It may be described as consisting of two 
portions, one in which the constituent cells are free, entirely separate from each other, 
or only fused together in very small groups, and another in which the cells are com- 
pletely fused together so as to represent either simple undilated tubes, or tubes irre- 
gularly constricted and bulged at intervals ; the former is evidently that part of the 
organ where the production of fresh cells takes place ; these are seen at first as 
granular cells with envelopes more or less distinct, but having only imperfect traces of 
nuclei ; subsequently the characteristic biliary spherules appear in them, and at last 
fill them completely. Now the cells becoming developed in this manner (and they 
proceed exactly in a similar manner in the Earthworm) may either become fused 
together to constitute the tubes above described, or they may lose all trace of an en- 
veloping membrane ; their component spherules separating from each other, and the 
cell at last undergoing complete disintegration on the spot where it had been originally 
formed, while its elaborated contents are probably absorbed into the circulating 
stream, from whence as plasma they had proceeded. The contents of the tubes are 
doubtless poured into the intestine, while the debris of the free parenchymal cells 
are scattered throughout the surrounding tissue, and thus in this low Annelide we 
seem to recognise a division of the hepatic apparatus into two portions, similar to 
those which we shall shortly distinguish in the higher animals ; these have probably 
separate functions, the tubular influencing by its secretion the intestine and its con- 
tents, while the parenchymal seems adapted to supply material directly for the use 
of the respiratory process. 
In the Arenicola, the biliary cells are of a lighter colour than in the Leech or 
Earthworm ; they are at first of a pale granular aspect and often exhibit nuclei ; 
subsequently they acquire dark oily-looking contents, and often change their form, 
becoming remarkably elongated ; their diameter varies from y- Q^o q to g^th of an inch. 
If the outer surface of the intestine be examined with a low power, it is found to 
present the convexities of numerous short sacculi with intervening furrows, and to 
be perfectly even and defined, while the inner surface, on the contrary, has a floccu- 
lent, almost ragged appearance. This effect is due to the disposition of the cells, 
which form a moderately thick stratum, resting on an homogeneous membrane, the 
sole constituent of the intestinal wall ; the cells are therefore actually in the cavity 
of the intestine, and in immediate contact with its contents ; they contrast herein 
remarkably with those of the Earthworm, which we have seen to lie on the outside, 
for the cells of the Sandworm may be completely removed by washing the inner 
surface of the intestine, while those of the Earthworm can be thus detached only 
from the exterior. 
These three instances from among the Annelides seem to exhibit the extreme varieties 
of condition which the hepatic apparatus is capable of assuming. In the Earthworm 
