History of British Entomostraca. 139 



solely destined for locomotion."* In both these suppositions we 

 shall find he is quite correct. 



Anatomy. — The shell in almost every respect strictly resembles that 

 of the Cypris, but from their general opacity and minuteness, it is ex- 

 ceedingly difficult to examine with precision the body of the inclos- 

 ed animal. After repeated attempts, however, to break down the 

 horny opaque shell, I succeeded so far as to discover that, like the 

 Cypris, the body of the insect is divided into two parts, connected 

 with each other by a narrow space, the anterior half containing the 

 eye, antennae, anterior feet, organs of mouth, and two pairs of in- 

 termediate feet ; the posterior half containing the posterior feet, and 

 a short appendix or tail. The eye resembles in appearance and si- 

 tuation that of the Cypris, being single, fixed, and in the form of a 

 black sessile point. Antennae two, (Plate V. Fig. 16. a, a. Fig. 18.) 

 composed each of five articulations, furnished with one or two short 

 setae at the base of each of the three last articulations, and termi- 

 nated by three or four rather longer hairs at the extremity of the 

 last joint, differing very much in this respect from the same organs 

 in the Cypris. As the Cythere has never been seen to swim, these 

 organs may be thus considered as true antennae. The feet are de- 

 cidedly eight in number ; the anterior pair are inserted immediate- 

 ly beneath the antennae, and are by far the strongest of all, (Plate 

 V. Fig. 16., b. b. Fig, 19.) They differ in shape from the other pairs, 

 being flatter and falcated in appearance. They consist of four arti- 

 culations ; the first and third being very short. The last gives off 

 from internal edge three spines, and is terminated by two or three 

 short hooks as in the Cypris, while from the base of the second joint 

 there springs a long stiff seta, equalling in length the two last joints, 

 and being divided into three articulations, of which the middle is 

 the longest. This seta is mentioned by Muller as occurring in his 

 Cythere lutea, but is taken notice of by him as being peculiar to it, 

 or at least as not having been seen in any other species. It occurs, 

 however, in all I have examined, and seems to take the place of the 

 pencil of long hairs that is to be found on the penultimate joint of 

 the corresponding pair of feet in the genus Cypris, but the precise 

 use of which I do not understand. The three other pairs of feet 

 (Plate V. Fig. 16, c. Fig. 20.) are exactly like each other, except in 

 length ; they are round and slender, and consist each of four articu- 

 lations, the first of which is the largest, and gives off a short spine 

 at its base ; the last is the shortest, and is terminated by a long 

 curved hook. The first or anterior pair are, as in the Cy prides, di- 



* P. 387. 



