STUDIES ON THE DIGENETIC TREMATODKES. 4A7 
joined by the common yolk-duct. The shell-gland lies close 
to the left side of the ovary and receptaculum. Itisa small, 
compact structure with cells measuring ‘015 mm. and nuclei 
0058 mm. The cells have a distinct staining reaction, taking 
on a uniform dull red or reddish-purple with hzmalum-eosin. 
The small yolk-reservoir lies dorsally in the middle line of 
the body just in front of the anterior testis. The yolk-glands 
are lateral, extending from the pharynx to the posterior end 
of the body, where they unite behind the testes. Anteriorly 
a few follicles find their way across the middle line under the 
dorsal surface, but none ventrally. Posteriorly the follicles 
lie under both the dorsal and ventral surfaces and surround 
the intestinal diverticula. They are of moderate size, compris- 
ing twelve to twenty cells, which measure about ‘025 mm. in 
diameter, and have large (006 mm.), round, central nuclei. 
The uterus is limited in extent, being confined between 
the ovary and the posterior border of the ventral sucker, but 
also filling up the space between the sucker and the left 
intestinal diverticulum. The vagina is shorter than the cirrus- 
pouch, lying to the left of it and slightly dorsal. Its diameter 
diminishes from *035 mm. to *023 mm. It has the usual 
muscular structure with numerous accompanying myoblasts. 
The ova are not numerous (about sixty). They are light 
yellow, with a very thin shell. Their shape is broadly oval, 
but at the anopercular pole there is a small excrescence of the 
shell forming a small knob-like projection.! This is of variable 
size and is sometimes absent. It might be regarded as indicat- 
ing an initial stage towards the filamented condition of the ova 
in Helicometra. They measure ‘0715—0746 mm. in length 
by °039—0435 mm. in breadth. Average ‘073 by *041 mm. 
From Anarrhichas lupus six species of Distomids have 
at one time or another been recorded. The first of these are 
two species mentioned by Rathke* and named by Rudolphi* 
Distomum incisum and D. anarrhiche lupi, found re- 
1 For directing my attention to this I am obliged to Miss Lebour. 
2 «Dansk. Selsk-Skrift,’ v (1), (1799), p. 70, pl. 2, figs. 3, a, b. 
3 *Entoz. Hist. Nat., ii (1), (1809), pp. 361, 435. 
