522 MR. F. E. BEDDARD ON THE DEVELOPMENT AND [Deec. 7, 
Ceratodus, is the resultant of a large number of cells the protoplasm 
of some of which undergoes certain changes and forms a more or 
less fluid mass with the original nuclei suspended in it ; this mass 
appears around and between the rest of the cells, which are destined 
for its nutrition. The whole structure is surrounded by a definite 
follicular layer, which also shares in its nutrition by the formation of 
olk in its cells and their proliferation inwards. These bodies are 
surrounded by cellular layers which correspond exactly to the layers 
which surround the ova of other vertebrates; the difference is that 
instead of there being a single cell which grows at the expense of the 
rest, the interior of the mass is formed by numerous cells, all equi- 
valent. 
The bodies may be distinguished as multicellular or plasmodial 
from the ordinary unicellular ova. The share which the follicular 
epithelium takes in the nutrition of the ovum, I have discussed in 
detail in my former paper and need not refer to it again here, except 
to remark that the elaboration of food-material in the follicular layer 
and its absorption by the ovum has of course no relation whatever 
to my view that the ovum is a cell-complex. Certain writers have 
adduced arguments of this kind as a disproof of the unicellular nature 
of the ovum, which to my mind have no force. 
On the other hand, the developmental facts with respect to the 
cells within the follicle appear to me to be difficult to interpret 
otherwise than on the assumption that the ovum has the value of 
more than a single cell. 
It is true that I have been unable to detect any earlier stages than 
the one figured on Plate LII. fig. 1; but the intermediate stages 
between that and the mature ovum are fairly complete. The dis- 
covery of the earlier stages is of great importance; it would decide 
among others the very important question whether the central mass 
of cells is, or is not, derived from primitive ova recognizabie as such 
in the germinal epithelium, and whether or not the central mass of 
cells is formed by the migration inwards of a number of these cells 
or by the repeated division of one. But, whatever may be the 
answer to these questions, I have, I think, proved that the ovum is 
formed out of this central mass of cells. Some of these cells are 
apparently used as pabulum, but others fuse together into a mass 
of semifluid substance, which bears a very close resemblance to the 
liquor folliculi of the mammalian follicle. The resemblance is still 
more striking if we accept Waldeyer’s statements that the liquor 
folliculi is produced by a direct metamorphosis of the follicular cells, 
their nuclei remaining, as in the case of Protopterus, suspended in 
it. This substance, however, in Profopterus has not a mere passive 
function, serving, as in the mammal, to aid in the expulsion of the 
ripe ovum, possibly also in its nutrition ; it retains the activity of the 
cells from which it is derived and secretes yolk ; it must therefore 
be looked upon rather as a plasmodium of these cells than a product 
of their degeneration, although its deep staining with borax carmine, 
as opposed to the very light staining of the remaining cells, indicates 
some chemical change. Furthermore, there is no evidence of any 
