THE DEVELOPMENT OF THE SPERMATOZOA. 417 
viscid protoplasm of the spermatoblast; but the nucleus 
does not undergo any corresponding increase in length, it is 
only reduced in size as division proceeds, and finally assumes 
its mature pyriform shape. 
Before any sign of commencing elongation of the plasma 
is visible, the nucleus appears at the pole of the spermato- 
blast, next to the blastophoral cell; and soon after this, 
from the opposite pole, there may be seen a fine whip of 
protoplasm, which consists of a proximal short, stiffer por- 
tion, terminating in a slight knob, and a distal, very fine 
lashlike part, which requires a good light to make its 
presence recognisable. 
This filament is visible at the extremity of the spermato- 
blast for some time, but appears to be absent in the mature 
spermatozoon. It seems as if it served as a guide to the 
elongating plasma, and became itself swallowed up in the 
process as it nears completion. 
This elongation of the plasma seems to be a kind of flow- 
ing down of the semi-viscid substance, for sometimes the 
greater part of it is found as an irregular or roughly spheri- 
cal drop collected at the distal end of the spermatoblast ; at 
other times it elongates, as a whole, with various swellings 
in droplike beads at the distal end, giving it a monilliform 
appearance. 
Division of the nucleus appears to continue after the 
external plasma has commenced to “ drop,” as the mass is 
not always divided below in correspondence with the nuclear 
heads; it is not uncommon to find two or three heads 
connected with a common mass of protoplasm, from the 
distal end of which there is commonly to be seen a corre- 
sponding number of lashes. 
As regards the fate of the blastophoral cell after the sper- 
matozoa have left it, I have no observations to offer; but if 
one may judge by what occurs in other divisions of the 
animal kingdom, it is extremely probable that it atrophies. 
Rana.—Siructure of the testis and arrangement of the 
vasa efferentia.—Though the frog is such a common animal, 
and its anatomy so perpetually studied, there is not, so far 
as I am aware, a figure or concise description of the testis 
and its efferent ducts in this language. I therefore append 
a diagrammatic woodcut of the right testis (v.) and a 
portion of the right kidney (4.) with the following 
description : 
Spengel, in his ‘‘Urogenital System of Amphibia,” published 
in ‘Semper’s Arbeiten,’ vol. iii, gives an account of the 
testis and its ducts as found in Rana, and from this my 
