of Edinburgh , Session 1885 - 86 . 
819 
form ,a cover cell for the whole, there seems no difficulty in regarding 
the term sperm-morula applied to such a case as in the truest way 
descriptive, and in regarding the process as distinctly homologous 
with that which occurs in the regular and total segmentation of the 
ovum (fig. A', A"). 
(6) The division of the mother-sperm cell is not, however, always 
equal, but forms occur, e.g., in Plagiostome fishes, where one cell pre- 
dominates in size over the other (B', B // ), a phenomenon which admits 
of ready comparison with such a phase of unequal ovum-segmenta- 
tion as is represented in fig. B, where the morula consists of a large 
number of small cells, and of one somewhat predominant yolk-filled 
cell. 
(c) The not unfrequent form of spermatogenetic segmentation 
which Blomfield has described in the earthworm, where the incipient 
sperm-cells enclose a more or less large undivided mass, at once 
suggests a comparison with the centrolecithal segmentation as exhi- 
bited, for instance, by a Peneus ovum, where the formative cells 
surround the central yolk-mass. And just as in cases of the latter, 
the individual cells are sometimes seen not very well defined off 
from the central nutritive mass, so is it also in various forms of 
spermatogenesis (fig. C', C"). 
( d ) Just as it was seen that, in those forms of sperm-segmentation 
which are directly comparable to morulse, one cell might predomi- 
nate in size over the others (fig. B' B ") ; so forms occur (see 
Gilson, &c.) where the sperm-cells are borne on the surface of a 
large undivided mass (fig. IV, D"), forming as it were a blastodermic 
plate, as seen in forms of partial ovum segmentation where the 
formative cells appear round one pole of the large undivided yolk- 
mass (fig. D). 
(e) Between the last-mentioned case and that described by Yon 
Ebner there is but a step (fig. E', E"). The nucleated lappets, which 
he has described as crowning the large nutritive blastophore, differ 
but little from the formative cells just referred to, except in the 
indefiniteness of their separation from the nutritive mass, a 
phenomenon which also finds its parallel in stages of partial ovum- 
segmentation (fig. E). 
(/) In another form of spermatogenesis, observed for example 
by Semper in the Rays, the spermatocytes were found to be sunk 
