168 M.T. Thorell on two European Argulide. 
along the middle line of the upper surface of the adult animal, 
and is marked on either side of this median line with large dark 
spots, arranged in rows. In the sae which is formed by this 
membrane the eggs are closely packed together, sometimes 
rather firmly attached to each other, sometimes apparently quite 
free. They surround here a smaller, almost cylindrical organ 
(the true ovarium), to which the innermost eggs are firmly at- 
tached. I have sometimes found that this organ contained a 
large number of eggs in a very early stage of development, while 
those lying outside were fully matured. I conjecture that these, 
after they are laidand sufficiently matured, becomesevered from the 
spot where they were formed, and so come to be immediately en- 
closed in the outer membrane of the ovary. Thus Leydig’s sug- 
gestion that the ovaries in A. foliaceus are ‘a simple bag” does 
not apply to A. coregont. 
‘The number of the matured eggs is very variable. In a large 
specimen I have reckoned about 350 points. In appearance 
they are exactly like the eggs of A. folzaceus. Their length is 
about 4, their breadth about 3 millim. The receptacula seminis 
are situated, as in A. foliaceus, at the base of the tail. They 
have the form of an almost spherical bladder, from which a long 
channel of communication, with thick walls and a very narrow 
passage, proceeds to a conical papilla situated im a concavity on 
the side and somewhat behind the mouth of the ovary. In this 
passage, rather nearer to the papilla than to the receptacle, 1s the 
commencement or opening of another blind, crooked canal, spiral 
towards the end: in A. foliaceus two such canals are found. 
The receptacle itself is, im young specimens, perfectly empty, but 
in the older ones it contains another bladder, of a darker colour. 
Such is the case also in A. foliaceus, where, according to Leydig, 
this inner bladder first shows itself after pairing, and is full of 
spermatozoids. It seems to be perfectly closed, and may easily 
be taken out of the receptacle without breaking. Leydig asserts 
that its membrane is produced in A. foliaceus into a homo- 
geneous thread, which stretches through the channel as far as 
the tip of the papilla. I have not found such a thread in 4. 
coregont. The passage of this channel of communication pre- 
sents just the same optical appearance in individuals with or 
without the spermatozoid-bladder already mentioned ; and the 
passage of the accessory canal is perfectly lke that of this chan- 
nel. If such a thread as that which Leydig speaks of were pre- 
sent here, it would certainly produce a streak in the canal. 
Moreover, when the bladder is taken out, a portion of the 
thread would follow if such were really present; this, however, 
does not occur, and I have been equally unable to detect it by 
cutting asunder the channel of the receptacle. 
