THE DEVELOPMENT OF THE SPERMATOZOA. 419 
When isolated this canal presents a varicose appearance, 
and from each swelling may be seen a short tube running 
on the dorsal surface of the kidney towards the ureter, but 
it soon becomes lost in the substance of the kidney. The 
time at which to observe these canals and the whole course 
of the semen is in the spawning time, when by squeezing the 
gland the vessels become injected with spermatozoa and are 
conspicuous by their pure white colour. 
The urinary tubules into which these canals open, were 
determined by Spengel to be the collecting tubes or last part 
which runs transversely across to join the ureter, and so 
convey the semen to the exterior. 
There was no difference discernible in a tube which 
contained spermatozoa from that which had none. 
Development of the Spermatozoa.—The development of 
the spermatozoa of Rana will be most conveniently deseribed 
by taking the structure and contents of the testis at four 
different periods of the year, and from these compiling a 
complete history of the changes undergone. 
If the testis be examined any time from about the end of 
August or the beginning of September till the spawning 
time in the spring, it will be found to be full of bundles of 
spermatozoa arranged radially around the circumference of 
a testicular crypt (Plate X XV, fig. 1). 
If the contents of a testis be received and teased slightly 
in a drop of salt solution, and then exposed to the vapour 
of osmic acid and stained, these bundles will be seen to have 
taken up the staining fluid for the greater part of their 
length, which represents the nuclear part of the sperma- 
tozoon, while at one extremity of the bundle they taper 
away, generally ending in a slight knot, stained yellow by 
the picrocarmine, which represents the tail, and is at this 
stage, when observed fresh, in a state of vibration, like that 
of the mature spermatozoon. At the other extremity of the 
bundle is, in the majority of specimens, a mass of a non- 
stained substance, not granular, or very slightly so, which 
contains a spherical or ovoidal nucleus, and it was this body 
which, from its similarity to the blastophoral cell of Lum- 
bricus and Helix, first induced me to follow in detail the 
history of the development of the spermatozoa (Plate XXV, 
figs. 2—6). 
This body is not found attached to every bundle, but, as 
the subsequent history will show, it is extremely natural 
that it should not always be present, as it is left behind 
when the spermatozoa are shed, and in many cases it would 
be detached during the slight teasing which is necessary to 
