438 Cells in the Ovum compared with Blood-Corpuscles. 
discern in the pellucid nucleus of the yolk, dividing and giving 
origin to two yolk-cells, according to the German author, the 
hyaline nucleus of Dr, M. Barry*.” 
3. Professor Rudolph Wagner observed that the size of the 
blood-corpuscles in the naked Amphibia is “so much the 
larger, the longer the gills continue in the larval state.” Thus 
the blood-corpuscles are larger in the Newt than in the Frog, 
He hence conjectured that the Proteus and Siren, because 
they permanently have both gills and lungs,—being there- 
fore permanently larvae,—would be found to have the largest 
blood-corpuscles. In the Proteus he had the opportunity of 
seeing the idea realized +.—This connexion between the size 
of the blood-corpuscles and a larval condition of the animal, 
I believe has not been explained. 
4. On first seeing the large cells in the mammiferous ovum{, 
I was struck with the resemblance they bore to the corpus- 
cles or cells of the blood in, for instance, the Batrachia; which 
was also remarked by Dr. Roget on seeing my delineations of 
the former: and I have since (§ 1, 2) shown them to be per- 
petuated by the same means. Finding also in the blood of the 
mammiferous embryo corpuscles or cells (figs. 4, 5) like the 
ordinary blood-corpuscles or cells of the adult Batrachia, &c., 
I conceived that the difference between the condition of the 
blood-corpuscles in the embryo and in the adult of the same 
animal, was referable to a difference in the degree of their 
development as cells§. 
5. Now there are facts, I think, which leave little doubt 
that the blood-corpuscles—not only in the embryo, but at 
all periods of life—are descended from the two cells consti- 
tuting the foundation of the new being in the ovum; cells 
arising out of previously existing cells, by self-division of the 
nuclei. 
6. When tracing the early stages in the formation of the 
embryo, I showed that, as the cells thus increase in number, 
they diminish in their size. Have we any proof that this di- 
minution in size ceases in later stages? Is it not rather to be 
presumed that it continues? and, indeed, does not the differ- 
ence in size between the corpuscles of adult and foetal blood 
render it probable that this progressive diminution in size 
goes on? If so, the younger the larva is, the larger may be its 
* Hunterian Lectures, by Professor Owen, F.R.S., from Notes taken by 
W. W. Cooper, M.R.C.S. 1843. No. 3. p. 78. 
+ See Proceedings of the Zoological Society, Nov. 14, 1837. 
{ Researches in Embryology, Second Series. Phil. Trans, 1839. pl. 16. 
fiz. 1053, &c. 
§ On the Corpuseles of the Blood, Part [I. Phil. Trans. 1841. p, 206. 
