Hiriidinea. 
171 
to study the internal anatomy in determining the boundaries of somites. A careful 
investigation of the nervous system of one specimen, which can not be described here 
in detail, gave the following results : — 
Somite. 
I, II, III 
IV. V 
No. 
VI— XXIV 
XXV 
XXVI, XXVII 
of annnuli. 
I 
2 
• 3 
. 2 
I 
The first five and last two annuli are incomplete ventrally, being comprised in the 
formation of the anterior and posterior sucker respectively. 
The head consists of seven annuli (somites I— V). It is decidedly broader than 
the neck and looks, when viewed from above, somewhat like that of Hemiclepsis 
marginata. The oral sucker occupies the ventral side of the first four somites, while 
the two annuli composing somite V are fused ventrally to form its posterior boundary. 
The mouth-opening is situated in the middle of the slightly concave sucker. 
The eyes are wanting completely. No trace of eye-like organs could be detected 
even in sections. 
In three of the specimens (nos. i, 2 and 4) a part of the proboscis, ranging from 
I "5 mm. to 2 8 mm. in length, was seen protruding from the mouth-opening, so that 
the tinty hooks so characteristic of the genus could be observed externally. They are 
three in number, and are arranged radially round the anterior end of the proboscis a 
short distance from the tip (pi. vii, fig. 9). One is median and dorsal, the other two 
ventro-lateral. They are of a conical shape, sharply pointed, and are directed ob- 
liquely backwards; measured on the outer side they are about 0-25 mm. long. As the 
proboscis on which they sit is only 0 2 mm. thick, the hooks appear quite conspicuous 
under the microscope. As to the function of these organs I am at present unable to 
say anything, though it seems highly probable that they serve as an apparatus for 
attachment. 
The genital orifices are situated one somite further back than in most of the 
Glossiphonids. The male aperture lies near the posterior margin of the 28th annulus, 
i.e. just in front of the furrow separating somites XII and XIII ; the female one ring 
further back, i.e. in the furrow between the first and second annuli of somite XIII. 
They are both inconspicuous, as their position is not indicated externally by any prom- 
inent structure, such as elevations, glandular patches, etc. The clitellum was not 
discernible in any of the specimens. 
I was not able to detect the nephridial pores externally, but in sections they were 
found to open in the furrow between the first and second annuli of certain somites. 
The posterior sucker is quite small and flat. It is circular as usual, with the dia- 
meter less than one- third the breadth of the slender trunk. It is directed obliquely 
backwards and downwards, and is attached chiefly to the ventral side of the last 
annulus and partly also of the last but one. Evidently the sucker is not of such vital 
