ITS DIFFERENT PHASES OF DEVELOPMENT IN THE ANIMAL SERIES. 65 
as in general appearance ; the only difference being that its nucleus is cellseform, 
whereas that of the red corpuscle of the Frog is, as we shall find, rather solid- 
looking. The red oval corpuscle of the blood of the Skate under consideration, I 
propose to name nucleated blood-cell, in contradistinction to the granule-cell, which, 
though also nucleated, is not in general discovered to be so until after the solution 
of the granules by acetic acid, and which in consequence of its being filled with 
granules is otherwise well designated granule blood-cell*. 
11. Besides the two kinds of cells which I have now described in the blood of the 
Skate, there are others which, on account of their paleness, do not at first attract 
so much attention, but which it is of the greatest importance particularly to notice. 
12. One kind (fig. 4 a.) has the characters of the granule-cell, only the granular 
contents are very fine and do not so strongly refract the light, hence its paleness. 
This pale granule-cell I consider an advanced stage of the dark-looking granule-cell. 
This latter I will call the coarsely granular stage, the former the finely granular 
stage of granule-cell. 
13. Another kind of the corpuscles referred to, has essentially the same structure 
as the red nucleated blood-cell above described, being a cell containing in its interior 
a cellseform nucleus (fig. 5 a.) ; the only difference is that both cell and nucleus are 
circular (the former' about xsVoth of an inch in diameter, the latter about 3 - 0 ] 00 th), 
and that the cell is either destitute of colour or but slightly tinged red. 
14. That this circular nucleated cell is an early stage of the oval red nucleated 
cell is shown by the circumstance, that besides it there are cells having the same 
structure but more or less oval-shaped, and still either altogether uncoloured, or 
slightly tinged red (fig. 6.), which evidently form a transition to the oval red nu- 
cleated blood-cell. 
15. Two stages of the nucleated blood-cell may thus be recognised, an uncoloured 
and a coloured stage. 
16. The description now given of the nucleated blood-cell of the Skate in the un- 
coloured stage, and a comparison, of figures 5 a. and 2 b. will show that it resembles 
the granule blood-cell after its granules have been dissolved by the action of acetic 
acid ; the only difference being that in the former the cellseform nucleus is larger 
and more developed. 
17- This resemblance, and the circumstance that corpuscles occur in which the 
cellseform nucleus is large, but still surrounded by a few granules (fig - . 4 b. ; see also 
the corresponding corpuscle in the Lamprey, represented in fig. 2.), and which may 
be viewed as a transition from the granule to the nucleated cell, go to prove that the 
nucleated blood-cells are developed from the granule blood-cells — are, in fact, the 
granule blood-cells with the cellseform nucleus developed, at the expense of the 
granules which have disappeared. 
* name “granule-cell” I have borrowed from Professor Vogel of Gottingen, who first employed it to 
designate a form of cell which is developed in inflammatory exudations. 
K 2 
