BRANCHIOPODA. 127 



however, to be very common in the marshes and ponds of the North, 

 vi^here it aggregates in considerable numbers. In the 



Daphnia, Mull. 



The oars are alvs^ays exposed to their base or to the origin of their 

 peduncle; they are as long, or almost as long as the body, and are 

 divided into two branches, the posterior of which consists of four 

 joints, the first very short, and the other, or the anterior, of three. 

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

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

 fore it, which Muller considered as a second eye(l). 



Although the extreme smallness of these animals might be sup- 

 posed 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, 

 Schaeffer, 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 with the greatest success. 

 The mouth is situated beneath at the base of the rostrum; we con- 

 sider (with Randohr) the inferior portion of the head, which Straus 

 denominates a labrum, as an elongated clypeus, and we apply the for- 

 mer 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 jaws(2) terminated 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 



(1) 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. Schaeffer had previously noticed it. 



(2) 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. 



