298 
A. G. bourne. 
a very distinct cuticle, which in sections of hardened prepara- 
tions is often seen in a state of desquamation (fig. 6). 
In these large ductules too, in fresh (and therefore still 
living) excised nephridia, I have studied the contained liquid. 
It is perfectly colourless and transparent, but frequently 
contains structureless globules (fig. 12) which, by pressure, 
can be made to move along the series of ductules. 
The cells of the testis lohe (fig. 2, t. l.) agree altogether 
in structure with those of the apical lobe, having medium- 
sized ductules which are branched to a small extent, the 
branches being continuous, not csecal. In each cell the 
ductule gives off some two, three, or four branches of the 
same calibre, and each of these is continuous with a similar 
branch of the ductule in a continuous cell. 
Communications of the ductules of different lobes with 
one another . — The diagram (fig. 1) will serve most satis- 
factorily to explain what I have ascertained on this point. 
The ductules of the testis lobe do not directly communicate 
with those of the adjacent apical lobe, but run on through 
the short bit of gland joining testis lobe and main lobe, and 
then gradually pass into the finer kind of ductule which is 
found throughout the main lobe. There is no junction at 
the apex of the main lobe (near th^ word inferior vein” 
in the diagram) between the ductules of the main lobe and 
the ductules of the apical lobe, which is all the more re- 
markable since the central duct is here continued from the 
one lobe to the other. On the other hand, at the point 
where the recurrent piece ” joins the concavity of the 
main lobe, as seen in the figure, there is an extensive com- 
munication of the large ductules of the recurrent piece ” 
with the ductules of the main lobe. 
VI. — Blood-vessels and Tunic of the Gland. 
The mass of cells which forms the glandular portion of 
tlie nephridium, with its various lobes, is held together by an 
investment of fibrous tissue, and is further beset by a large 
number of blood-vessels which, running longitudinally on 
the superfices of the gland, give off branches which pene- 
trate the mass of cells at numerous points, and form within 
the cell-mass one of the most complete inter- cellular blood- 
plexuses known to exist, and resembling that of the Mam- 
malian liver. 
The investing fibrous tissue of the gland I shall not 
describe in detail. It is dealt with by Professor Lankester 
in an article On the Connective Tissues of the Leech,” 
published in the present number of this journal. It will be 
