376 M. T. Thorell on the Systematic Position 0/ M<? Argulidte. 



side this another stout vesicle, which is filled with spermatozoids. 

 A homogeneous sharply defined thread shows itself as a con- 

 tinuation 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 efiecting 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 in living 

 Argulids. Especially suitable for such researches is the large 

 Argulus coregoni, which would seem to be tolerably frequent in 

 the larger lakes of Sweden. 



Proper to the Argulidse is moreover the circumstance that the 

 eggs 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 ^. 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 

 Argulidai 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 



