520 MR. F. E. BEDDARD ON THE DEVELOPMENT AND [Dec. 7, 
state of preservation, but in most cases the nuclei were very well 
preserved indeed, showing the rounded or oval form and the granular 
contents. This will not apply to the germinal vesicle of the ova, 
which were usually rather altered, showing, however, the peripheral 
layer of germinal spots. It does not seem likely, therefore, that the 
structure just described has been so altered as to render its identi- 
fication impossible. 
As already said, the evidence of the existence in Ceratodus of 
the structure formed by a fusion of cells depends upon only one 
case, which is an early stage corresponding to that of Protopterus 
figured on Plate LIII. fig. 9. This is the only example that 
I have succeeded in finding after a careful examination of many 
hundred sections. Besides these, my sections of the ovary contain a 
few peculiar structures, displayed in figs. 3, 21-23, which are cer- 
tainly not referable to the same series as the last, and concerning 
the nature and homologies of which I am in great doubt. The 
material at my disposal was not sufficiently well preserved to enable 
me to speak with certainty as to every detail of structure; and I only 
succeeded in finding a very few of the bodies in question, so that the 
following account is necessarily meagre. 
In fig. 3 of Plate LII. is represented what I believe to be the 
earliest stage: it consists of a spherical mass of cells bounded 
externally by an apparently structureless membrane, which separates 
them from the surrounding ovarian stroma (a); the cells are mainly 
disposed round the periphery of the sphere, the centre of which 1s 
largely oceupied by spaces in which there is no trace of any fluid ; 
the cells are small and rounded, with a large spherical or oval nucleus ; 
the nucleus, but not the cell-protoplasm, is deeply stained by the 
reagent used (borax carmine). The cells are exactly similar to the 
germinal cells so far as I could see; and the conditions I shall 
describe in the next stage lead me to infer that they are derived 
from the germinal epithelium. 
The second stage differs from that just described in being still 
continuous with the germinal epithelium; this fact would seem to 
point to its being an earlier stage than that just described, were it not 
for another difference in its structure. The body consists, like the 
last stage, of a mass of cells, but in the interior is a patch of gra- 
nular substance, which shows a different reaction to the staining- 
fluid. It is bardiy at all affected by the borax carmine and has a 
yellowish tinge. This central mass encloses here and there a few of 
the more peripherally-placed cells. 
Of the next two stages, displayed in figs. 21-23, I am uncertain 
which ought to be regarded as the earlier. 
In both the mass of ceils has dwindled down to a single layer of 
peripherally-placed cells (6), which, as before, are separated from the 
stroma of the ovary by a conspicuous and apparently structureless 
membrane. In the centre of the cells is a spherical or oval mass of 
a substance somewhat granular in appearance, which is not separated 
from the peripheral layer of cells by any membrane, but only by 
shrinkage. This mass (figs. 2] and 22) is of a yellowish tint, hardly 
