478 PROF. G. GULLIVER ON | June 15, 
Considering therefore all the fore-mentioned disturbing circum- 
stances, perfect agreement and precision in measurements of the 
corpuscles, and deductions of completely unexceptional averages 
therefrom, by various observers, or even by one observer, will appear 
hopeless. Accordingly, as already hinted, my Tables cannot pretend 
to absolute exactness, and are only offered for what they may be 
worth ; and in the estimation of their value, allowance should be made 
for errors, whether instrumental or personal, more or less inevitable, 
notwithstanding the greatest care, in observations so extensive. 
But the relative value of the measurements, though probably not 
unexceptionable, may be entitled to more confidence as fair approx- 
imations to the truth. They were all made by me, under the same 
conditions and by the same means as described in former papers ; 
and by any valid micrometry, in spite of little mistakes or of vari- 
ations in the dimensions of the corpuscles of this or that species, the 
comparative results will appear sufficiently uniform. Thus, if we 
compare the red blood-corpuscles of species of one order or family, 
e.g. Tragules and other Ruminants, the corpuscles in the former 
animals will constantly prove the smallest—so, too, in Paradoxurus 
and Canis, in Hippopotamus and Elephas, in Mus and Hydrocherus, 
in Dasypus villosus and Orycteropus capensis, in Rhea americana 
and Casuarius javanicus, in Zootica vivipara and Anguis fragilis, in 
Bufo viridis aud Bufo vulgaris, in Osmerus eperlanus and Salmo 
salar. And in like manner the facts are equally clear in a com- 
parison of the different orders; so that the corpuscles are smaller in 
Ruminantia than in Rodentia, in Marsupiata than in Edentata, in 
Granivoree than in Rapaces, in Anura than in Urodela, in Sturiones 
than in Plagiostomi. 
PyRENZMATOUS VERTEBRATES. 
Tn every animal, without any known exception, of this great division 
the red blood-corpuscle is characterized by the presence of a mucleus, 
which is plainly demonstrable in the majority of the corpuscles when 
examined on the object-plate under the microscope. Nor is the tax- 
onomic value of this fact at all affected by the old and still vexed 
question, as to whether the nucleus exists distinctly or at all in the 
corpuscle while it circulates within the living blood-vessels, or is 
formed only after its exposure to the atmosphere or chemical re- 
agents. Many years ago De Blainville, Valentin, Henle, and others, 
and more recently Savory, supported the latter view; and the 
former was adopted by Mayer and K@lliker, to which Brunke has 
lately conformed. The subject cannot be entertained here; only it 
may be noted that I have satisfied myself of the substantial accuracy 
of Mr. Savory’s observations on the blood-disks of some British 
Batrachians, but not of the validity of his conclusion therefrom, and 
that I have plainly seen in certain fishes the projections on the cor- 
puscles, indicative of a nucleus, while they were flowing within the 
living blood-vessels. 
In Pyreneemata the thickness of each of the red blood-corpuscles 
is commonly about one third of its short diameter; they are oval, 
