284 
A. G. BOURNE. 
arrangements obtaining in Hirudo medicinalis, in order 
subsequently to compare with the nephridia of that form — 
those of Nephelis, Clepsine, and Pontobdella. 
I. — Current Statements as to the Nephridia of the 
Medicinal Leech. 
Omitting detailed reference to the writings of De Blain- 
ville, to Brandt and Batzeburg’s Medizinische Zoologie,” 
and to Moquin Tandon's valuable ^^Monographie de la famille 
des Hirudinees.” I shall here give brief extracts from Gra- 
tiolet, from Leuckart, from Leydig, and from Gegenbaur, in 
order to show what is the present state of our knowledge 
as to the nephridia of the Leech. 
In 1850 Gratiolet published a memoir in the French 
Academy’s series on the Circulation of the Medicinal 
Leech/’ and in 1862 another paper on this subject Ann. 
des Sciences Nat./’ Ser. iv, ^ Zool./ 1862). 
Gratiolet says : — The segmental organs, as Dr. Williams 
has called them, have been considered as appareils aquifer es 
(? water vessels), as tracheal or respiratory organs, or as 
mucous glands ; further, Dr. Williams {loc, cit.') has sug- 
gested that these segmental organs are the true ovaries in 
all the annelids. They are seventeen in number on each 
side of the body. Each is constituted by — 1. K tube with 
thick glandular walls. 2. A vesicle behind the tube, open- 
ing on the ventral surface of the animal by an excretory 
orifice. The tube is bent up into a narrow loop, the much 
attenuated branches of w^hich end by anastomosing; it is 
spread into a sling/ and then bent back into a right 
angle, one extremity of the ^ sling ’ being nearly vertical, 
the other directed horizontally forwards, and ending by being 
rolled on itself in a sort of bud, the first and much the 
thickest end being more or less dilated according to its 
position.” Gratiolet means by this that the t-wo halves of 
the lobe folded on itself, which forms the vertical portion, 
may lie close together, or be separated by an interval. 
He continues : — The two branches of the loop are 
similar in structure, the anterior differing from the posterior 
in having a canal at the lower end of the vertical part, 
which opens on the upper wall of the well-known oval or 
spherical vesicle. 
In front of the series of testes the upper parts of the 
loops are much dilated ; the lower part bends for^vards, and 
end in the above-mentioned bud; to this in the segments 
containing the testes is added a small coecal process, which 
