424, J. E. BLOMFIELD. 
tozoa, and, having performed this duty, undergo degenera- 
tion and disappear. 
We have seen that, in Rana, from one original cell more 
than one blastophoral cell is developed, and this seems to be 
paralleled by what takes place in Insects, as fig. 25, Plate 
XXIV, from Dytiscus, and figs. 26 and 27 from Pieris, will 
show. The exact origin of these cells in Insects I have not 
determined, but at the first glance they seem comparable to 
a large extent to the “ superficial nuclei” of Rana. 
> The literature on the development of the spermatozoa is 
very copious, more particularly that which treats of the 
development in Mammals, as may be seen by reference to 
the papers of von la Valette St. George in the ‘ Archiv fir 
Mikr. Anatomie.’ 
I do not propose to consider every individual publication, 
but to mention those who have put forward plans of sperma- 
togenesis capable of application to the whole, or at any rate 
large, divisions of the animal kingdom; but before doing 
this I may briefly state what my own views on the sub- 
ject are. 
A cell whose future destiny is male (spermatospore) com- 
mences to undergo changes which fit it for its new function, 
and by a process of multiplication gives rise to many ferti- 
lising elements. The first steps are division and multipli- 
cation of the nucleus, and a corresponding constriction of the 
surrounding plasma, till a multicellular mulberry-like mass 
(sperm-polyplast) is produced, which may be solid or hollow, 
consisting of young spermatozoa or spermatoblasts. During 
this process some portion or portions of the original cell 
cease to undergo further change and remain behind to 
support and nourish the developing spermatozoa (blasto- 
phoral cell). t 
The nucleus of the spermatoblast forms the head of the 
spermatozoon, and the tail is formed by the centripetal or 
centrifugal elongation of the plasma. When fully formed 
the spermatozoa are supported on the blastophoral cells till 
required and then shed off, leaving their supports to atrophy 
and decay. 
How far this view holds good for the Mammalia I am not 
able to say precisely, but the abundance of figures confirm- 
ing the above account in papers treating on this subject, 
justifies the idea (compare the account below of Meyer’s 
paper) that spermatogenesis will be found to be essentially 
the same in that class. 
Many of the figures show the blastophoral cell under 
various names, and represent stages which seem in most 
