8 
DR. C. H. JONES ON THE STRUCTURE, DEVELOPMENT 
follows. The liver appeared as a small grayish mass, consisting of delicate vesicular 
transparent cells, mingled with granulous and oily matter, not in great abundance. 
The gall-bladder was large, distinct, transparent, full of a colourless fluid, and lined 
by a distinct epithelium; it had a short duct communicating with the intestinal canal, 
from which an offset turned up to the mass of the liver ; this proceeded but a little 
way, and terminated by forming a small tract of nuclear particles. The resemblance 
between the structures observed in these young fish and those whose development I 
have traced above was so close, that I feel quite justified in concluding that the 
former presented the ultimate stage of the dev'eloprnental process, and therefore I 
venture to offer the following summary as descriptive of the formation of the liver 
and its excretory apparatus in Fishes. 
(1.) The intestine is formed before there is any trace of liver. 
(2.) The parenchyma of the liver and a vesicle, the rudiment of the gall-bladder, 
are first formed ; the small yolk mass lies in the substance of the liver. 
(3.) The gall-bladder assumes a pyriform shape ; its narrow end approaches the 
intestine and opens into it, while from a part of its extent hepatic ducts are developed 
that extend into the liver. 
(4.) The contents of the gall-bladder at first are not bile, but probably a weakly 
albuminous fluid ; this continues to be the case for some time after the parenchyma of 
the liver is completely formed. 
In my examination of the livers of Reptiles I have been more successful than 
formerly, and entertain no doubt of their being constructed exactly after the same 
plan as those of fish. The parenchyma in the Common Frog {Rana temporaria) 
presents no appearance of any lobular division ; it is often of very dark colour, owing 
to the presence of a black pigmentary matter ; it consists of delicate, large, feebly- 
formed nucleated cells, which have no well-marked envelope, and almost appear like 
masses of granulo-amorphous substance ; they are infiltrated with oil-drops, but 
present no bilious tint. There are also numerous free nuclei, and much diffused 
granular and oily matter as well as black pigmentary, which is in the molecular 
condition, and exhibits the peculiar to and fro motion. A considerable quantity of 
the black matter is in the form of spherical or oval corpuscles, which I described in 
my previous paper, and which have often a red or deep yellow tint. I supposed them 
at that time to be biliary concretions, but further inquiry has convinced me that such 
is not their nature, and that they are what I have termed them above, pigmentary 
formations. They are scarcely affected by the strongest reagents; liquor ammoniae, 
liquor potassae, sulphuric, nitric and muriatic acids leave them almost unaltered. On 
comparing them with the coloured corpuscles found in the spleen they appear quite 
identical, and I have little doubt are truly so; both I am inclined to think are 
pigmentary deposits, not necessarily derived from decomposing blood-globules. They 
do not occur in the kidneys, and are quite distinct from the ordinary ramifying 
pigment cells seen in other parts. I believe them to be a peculiar form of organic 
matter, rich in carbon, which not being eliminated from the blood in consequence of 
