BRANCHIOPODA. 249 



Their eye is small or punctiform, and, with tlie exception of certain 

 species, has not, as in Lynceus, the small black punctiform spot 

 before it, which Miiller considered as a second eye*. 



Although the extreme smallness of these animals might be supposed 

 to defy any attempt to investigate their organization, but few are 

 better known. Exclusive of those who have devoted themselves to 

 microscopic researches, four of the most profound naturalists, 

 Schaetfer, Randohr, Straus, and Jurine, Sen., the third particularly, 

 have studied them with the most scrupulous attention. If some 

 anatomical details escaped the notice of the latter, the omission has 

 been remedied by the labours of Randohr and Straus; Jurine also 

 completes the observations of the former with respect to their habits, 

 which he studied for a long period, and Avith the greatest success. The 

 mouth is situated beneath at the base of the rostrum; Ave consider (with 

 Randohr) the inferior portion of the head, which Straus denominates 

 a labrum, as an elongated clypeus, and we apply the former term to 

 that part which he styles the posterior lobule of the labrum. Directly 

 under it are two strong jaws — interior jaws of Randohr — without 

 palpi, vertically inclined, and applied to two horizontal jawsf termi- 

 tiated by three stout horny spines, in the form of recurved hooks. 

 Then come ten feet, the second joint of all of which is vesicular ; the 

 first eight terminate by an expansion in the manner of a fin, the 

 edges furnished with setae or barbed threads arranged like a crown or 

 a comb ; the two anterior seem to be specially appropriated to the 

 purposes of prehension, and in fact Randohr considers them as double 

 palpi, the external and internal ; they are the same parts, elsewhere 

 — Cyclops — called hands by Jurine. In the figures which they have 

 published, the terminal setae appear to be bearded : if this be so, we 

 do not see why these appendages may not concur in the process of 

 respiration :|:, a property confined by Straus to the following ones, 

 because the latter have, besides, a lamina on the inner side, which, 

 with the exception of the two last, is edged with a pectinated series 

 of setae, that according to the figures of Jurine and Randohr are also 

 bearded. The structure of the two last feet is somewhat different, 

 and Randohr distinguishes them by the name of claws. The abdo- 

 men, or body properly so called, is divided into eight segments 

 perfectly free between its valves, and is long, slender, recurved at 

 the extremity, and terminated by two small hooks directed backwards. 

 On the superior surface of the sixth segment is a range of four 

 papillae forming indentations, and the fourth presents a sort of 



* Such also is the opinion of Randohr, Monoc. pi. V, fig. II, iii, 6 ; and as he 

 discovered it in the Daphnia sima, it is possible that, although but slightly visible 

 in several species, this character may be common to this subgenus, and that of 

 Lynceus. Schseffer had previously noticed it. 



f The exterior jaws, in the language of Randohr ; Jurine not having separated 

 these parts from the preceding ones, supposed that the latter were accompanied by 

 a kind of valve and by a palpus. Hist, des Monoc. IX, f. 13 — 17. 



X According to Straus, CjT)ris and Cythere are not true Branchiopoda, inasmuch 

 as their feet are not provided with branchiae ; but, as we have already observed, the 

 setae and hairs of the two anterior ones and those of the antennae may exercise the 

 functions of branchiae as well as those of the pcilpi and first jaws. 



