M. T. Thorell on the Systematic Position of the Argulide, 283 
spot, placed on a perfectly similar trilobed projection from the 
brain-ganglion*. 
We have now gone through the proofs which have been put 
forward by Kréyer as grounds for the union of the Argulide 
with the siphonostomous Copepoda, and shown, we hope, that 
not one of them can be regarded as in any measure convincing 
or decisive. We will now briefly recapitulate the results to 
which we have been led during the foregoing investigation, and 
thence arrive at the conclusion respecting the systematic posi- 
tion of the Argulidz which those results seem to warrant. 
I. The Argulide correspond with the Copepoda generally, be- 
sides such points of their organization as are common to the 
Branchiopoda and Copepoda, only in these particulars :—that 
(1) The females possess receptacula seminis ; and that 
(2) Parthenogenesis seems never to occur. 
IT. But they differ from the Copepoda generally in the cir- 
cumstance that 
(1) Their limbs want the intermediate plate (mellanskifva), 
and do not show the form characteristic of Copepoda; that 
(2) They have two moveable eyes composed of numerous 
crystalline stemmata in front of the unsymmetrical larval eye ; 
that 
(3) The integuments of the head are developed into a bi- 
partite shield, very often covering the larger portion of the body; 
that : 
(4) The eggs are neither attached to external egg-sacs nor 
are received into a matrix when they leave the ovaries; that 
(5) Impregnation is not effected by means of spermatophores 
attached externally to the body of the female; and that 
(6) The larve leave the egg in a much more advanced state 
of development than in the Copepoda. 
III. Meanwhile they agree with the (higher) siphonostomous 
Copepoda in certain particulars, which all, however, depend upon 
their parasitic mode of life: they have, for instance, 
(1) A depressed body ; 
(2) A pair of the antenne modified as fixing-organs ; 
(3) The mouth transformed into a sucking-tube ; and 
(4) Strongly developed foot-jaws. 
IV. They differ likewise from the Siphonostoma in the follow- 
ing points :— 
(1) The first, not the second, pair of antenne are the fixing- 
organs ; 
* Vide Leydig, loc. cit. p. 39 &e. 
20* 
