290 
A. G. BOURNE. 
The sections were stained in some cases with haema- 
toxylin, but usually with E-anvier’s picrocarmine, which 
has a remarkable effect upon the naturally red-coloured 
haemal fluid. This very frequently is stained yellow by the 
picrin alone, whilst the surrounding tissues have a more or 
less complete carmine staining. Some very beautiful pre- 
parations were obtained by Mr. J. E. Blomfield by staining 
with two pigments in succession, viz. picrocarmine and 
anilin-blue. Oil of cloves and Canada balsam were used 
for clarifying and mounting. 
Camera lucida drawings, under a moderate power of the 
microscope (HartnacVs obj. 4), were now made of a complete 
series, giving all the sections in order in which any part of 
a selected nephridium was involved. Such a series of 
drawings compared with the whole nephridium, and with 
horizontal and transverse sections, has enabled me to 
thoroughly explore this somewhat tortuous and complicated 
body. 
III. — Form and Eegions of the Nephridium. 
The nephridium of tlie medicinal Leech is not the simple 
loop-like body with labyrinthine duct opening into a vesicle 
which it has been held to be, and^ such as it was drawn 
by Gratiolet. In the testicular region of the body the 
nephridium has the form which I have diagramrnatically 
represented in Plate XXIV, fig. I. It may be divided 
first of all into vesicle and gland, which are connected by 
the vesicle-duet. 
The gland is in the form of a thick made horse-shoe, 
the two limbs of which are elongated and produced till 
they meet. The front of the horse-shoe is dorsal and 
superior in the living Leech (to the right in the figure), 
whilst the produced limbs descend and are respectively 
anterior and posterior in position ; in the ventral region 
they are twisted out of the straight line in a forward direc- 
tion (see figure). From the forwardly placed thickened 
point of union of the two limbs of the horse-shoe reaches a 
delicate process which I call the testis lobe. It is 
more or less rudimentary in those nephridia which belong 
to the anterior region of the body where there are no testes, 
the further forward the nephridium the smaller is the testis 
lohe. 
The vesicle relatively to the form and position of the 
horse-shoe with its prolonged, and bent limbs may be said to 
balance the testis lobe. It lies posteriorly and ventrally rela- 
