M. T. Thorell on two European Argulidse. 167 



this point. That one of the anterior pairs of nerves runs into 

 the second pair of tootjaws^ that^ moreover, out of the lateral 

 bundles a nerve proceeds to each leg, and that the last (inner- 

 most) pair of nerves passes unbranching to the tail, I have, how- 

 ever, ascertained. No doubt certain stems proceed to the head- 

 shield, although I have not been able to follow them thither. 

 Of the two pairs of nerves which radiate from each of the second 

 to the lifth ganglia, the foremost, which is also the thickest, pro- 

 ceeds from the margin of the ganglion, the hinder one from its 

 underside. The nerves of the sixth ganglion are almost equally 

 strong ; those of one pair start from its side, those of the other 

 from its hinder margin. 



The ei/es seem to be entirely similar in structure to those of 

 A. fuliaceus. The number of crystalline cones I have found to 

 vary between 40 and 50. The single eye-spot consists of pig- 

 ment only, without crystalline bodies. 



The intestinal canal. — The narrow, chitinous gullet proceeds 

 in a bowed shape to the stomach, where it opens, by means of a 

 cup-like organ, into a cardia, which, however, is longer and 

 narrower than in A. foliaceus. The length of this organ is about 

 0*33, its greatest breadth 0"15, and its least breadth 009 millim. 

 The mouth of this organ is thickly set with papillae or obtuse 

 teeth. Before its entrance into this latter the gullet shows an 

 increase of width (its greatest diameter being about 0*06 millim., 

 its diameter where it enters the cardia about O'Ol' millim.). 

 The stomach itself is a short, spacious, posteriorly rounded 

 sac, which passes into the intestine between the first two pairs 

 of swimming-feet, being, however, distinctly separated therefrom. 

 On either side the stomach sends forth a strong branch into the 

 head-shield ; the further outbranchingsof this are not easily fol- 

 lowed in a specimen in spirits; aud therefore I cannot venture to 

 state whether such branches are directed outwards only, as in 

 A. foliaceus, or whether, as in A. purpureus, they proceed from 

 the larger stems inwards as well as outwards. 



The intestine extends as a spacious, gradually tapering tube 

 from the stomachal sac to the anal opening, which is situated 

 between the appendages of the tail. 



The heart or dorsal vessel I have not been able to separate 

 distinctly. I regard the tail as a respiratory organ which, on 

 its inner surface, shows a copious netwoi'k of muscular fibres, 

 the contractions of which keep the nourishing fluid in quick and 

 powerful motion. 



Generative organs. — In full-grown females the ovary forms an 

 oval mass, which extends from the base of the second pair of 

 footjaws to the base of the tail, where the opening is situated in 

 a low rounded projection. The surrounding membrane stretches 



