M. T. Thorell on the Systematic Position of the Argulide. 277 
here, while the seminal bladder and ductus deferentes lie in the 
trunk. In the Branchiopods both ovarium and testes have their 
position in the anterior portion of the tail *. 
While*we are on the subject of the sexual conditions of the 
Argulide, we must not omit to mention a circumstance which 
in some measure removes them from the Branchiopoda : propa- 
gation by means of parthenogenesis, which seems to be so general 
in that order, seems to be as rare among the Argulide as among 
the Copepoda. 
Among the anatomical characters whereby the Copepoda may 
pretty constantly be distinguished from the Branchiopoda, it has 
been asserted, is the absence of gall-secreting branches in the intes- 
tinal canal. Wowever, according to Claus, many Copepods, 
especially the genus Sapphirina, possess extremely strongly de- 
veloped glandular liver-appendages; and since these in many 
Branchiopoda (as, for instance, the Branchipodidz) are but 
feebly developed or (as in Limnadia and many Cladocera) alto- 
gether wanting, we must not attribute to this character any 
special importance. Still the strong branches of the intestinal 
canal beneath the head-shield in Apus and Argulus certainly 
afford further grounds for considering that these creatures are 
nearly related. ‘ 
Neither in the nervous nor circulatory system do I find any 
characteristics which might contribute to fix the line of demarca- 
tion between the Branchiopods and Copepods. The copious 
supply of blood in the head-shield in Argulus, which Zenker 
regards as attesting the Copepod nature of the Argulide, 
depends only on the strong development of this shield, the form 
of which meanwhile points, as has already been said, to a near 
relation with the Branchiopoda. According to Leydig and Claus, 
blood-corpuscles are wanting in the nourishing fluid of the 
Copepoda, but are found in both Phyllopoda and Cladocera, as 
also in Argulus. This difference, however, is not constant ; 
for they are found also, according to Dana, in abundance in the 
Caligide in the first-named order. The well-marked separation 
of the tail from the trunk, and its modification as a respiratory 
organ, would seem to be the most prominent feature in their 
* Leydig, “ Ueber Artemia salina und Branchipus stagnalis, Beitrag zur 
anatomischen Kenntniss dieser Thiere,”’ Zeitschrift fiir wissenschaftliche 
Zoologie, Bd. ii. p. 297 &e. Leydig is guilty of a misrepresentation when 
he says that Joly did not perceive the true ovaria of Artemia salina, but 
only the uterus, which he mistook for the ovary. Joly expresses himself 
thus :—‘ Sur les parties latérales des deux premiers anneaux de l’abdo- 
men on s’apercoit .. . deux sacs allongés, cylindriques, dont le fond est 
tourné du cété de la queue. Ces deux sacs sont les ovaires proprement diis. 
Ils viennent déboucher dans une matrice ou ovaire externe, qui parait étre 
une dilatation considérable de leur propre membrane.” 
