ITS DIFFERENT PHASES OF DEVELOPMENT IN THE ANIMAL SERIES. 69 
puscle, or nucleated blood-cell in the coloured stage of the Skate, as above mentioned. 
The principal difference between the cells in question in the two animals, is in the 
character and appearance of the nucleus ; whilst in the red cell of the Skate, the 
nucleus, though more or less oval, still retains its cellseform appearance ; in that of 
the Frog it is still more solid-looking and condensed than it was in the nucleated 
ceil in the uncoloured stage, and at last acquires the appearance as if consolidated 
by fusion into a small oval-shaped homogeneous mass. 
39. The development of the red oval corpuscle or nucleated cell in the coloured 
stage from the nucleated cell in the uncoloured stage, can be readily understood to 
take place by the latter secreting into its interior colouring matter, becoming at the 
same time enlarged, and all this in the manner above explained in regard to the red 
nucleated cell of the Skate. 
40. But as to the development of the nucleated cell in the uncoloured stage from 
the phase of granule-cell, this appears to take place in the following manner : — The 
cellseform nucleus of the granule-cell becomes developed into the solid-looking 
nucleus at the expense of the granules which disappear. As this takes place, the cell- 
wall contracts around the nucleus, becoming thicker and stronger, and by and by 
only becomes distended again by the accumulation of contents, as above described 
in the case of the Skate (par. 17-)*- 
41. The blood-corpuscle of the Frog in its phases of development, thus resembles 
in all essential respects the blood-corpuscle of the Skate. 
42. It would be supererogatory to institute a formal examination and comparison 
of the blood-corpuscle of any other oviparous vertebrate animal, but for the sake of 
what comparison may be desired, I have given figures of the blood-corpuscle of a bird 
in its different phases of development. 
43. I now come to consider the blood-corpuscle of Man and the Maminifera in its 
different phases of development. 
In the first place, it is to be observed that, as in the early embryonic state of the 
Maminifera, the red corpuscles of the blood are most of them very different from the 
red corpuscles of the blood in a more advanced stage of intra-uterine life as well as 
after birth, I will, in treating this subdivision of my subject, first examine the blood- 
corpuscles of the early embryo of a mammiferous animal, comparing them at the 
same time with those of the oviparous Vertebrata ; and then I will examine the 
corpuscles of the fully-formed blood of Man and the Mammifera, comparing them 
with those of the early embryonic blood of the same class, and also with those of 
the blood of the oviparous Vertebrata. 
* The probability of such a mode of development of the red corpuscle of the blood of the Frog from the 
“ lymph or “ colourless” corpuscle (granule-cell), has been already well-advocated by Professor H. Nasse 
and also by Dr. Baly in his translation of Muller’s Physiology. 
