276 M.T. Thorell on the Systematic Position of the Argulide. 
side this another stout vesicle, which is filled with spermatozoids. 
A homogeneous sharply defined thread shows itself as a con- 
tinnation of the skin of this enclosed vesicle, through the outlet, 
to a papilla situated in a concavity.” On the nature of this 
bladder nothing is said. But may we not see in this a sperma- 
tophore which is not, as in the Copepods, attached externally to 
the body of the female by means of a tubiform filament through 
which the spermatozoids pass into the receptacle, but which is 
altogether introduced into this latter? And if this supposition 
be correct, where is the spermatophore produced? Possibly, 
may we not think, in the capsule on the third pair of legs, 
whence it must be supposed to have become transferred to the 
receptacle ? in effecting which the “hook” on the last pair of 
legs would certainly play an important part. Or may not the 
two accessory glands which open each upon the lower portion 
of its own ductus deferens contribute the secretion to form the 
walls of the spermatophore? And how can the spermatozoids 
escape from this bladder or spermatophore if the channel of 
communication be filled up by a “ homogeneous thread” ? 
I have dwelt upon these circumstances chiefly with a view to 
drawing to them the attention of those who have opportunities 
and inclination to accord them a due investigation m living 
Argulids. Especially suitable for such researches 1s the large 
Argulus coregoni, which would seem to be tolerably frequent in 
the larger lakes of Sweden. 
Proper to the Argulide is moreover the circumstance that the 
eges come directly from the ovarium into freedom: they are 
neither retained in a “uterus,” matrix, or any structure ana- 
logous thereto, as is the case in most Branchiopoda; nor are 
they attached to the projection of some of the legs, as in some 
forms of this order. (See what we have said concerning the 
ovarium of A. coregoni, p. 168.) This is, however, of subordinate 
importance. The ovarium of Argulus may be regarded as cor- 
responding to both uterus and ovarium in, for example, Bran- 
chipus, forming, however, a single structure, in which the por- 
tions set apart for the producing of the eggs and for their main- 
tenance have not yet become separated in position from each 
other. 
The remaining peculiarities which the sexual apparatus of the 
Argulide presents are not of very great importance, and are 
always easily reducible to conditions commonly prevalent in the 
Branchiopoda. They are mostly to be accounted for by the fact 
that the tail is sharply separated from the trunk, whence also 
the various parts of the sexual apparatus are more separated 
from each other. Thus the ovarium is situated entirely in the 
trunk, while the receptacles are in the tail; the testes are placed 
