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Selecte& motes from tbc poetal (Wiicvo^ 

 0copical Societ^*6 IRote^Booke. 



Biaptomus castor. 



By Arthur Hammond, F.L.S. PI. XXII. 



AN Entomostracan found about April and May in weedy ponds 

 and ditches, and on which I have been recently making some 

 observations. These little creatures are of a reddish colour. The 

 females measure about one-eighth of an inch ; the males consider- 

 ably less. The latter sex may be at once distinguished by the 

 asymmetrical development of the long antennje, which consist of 

 twenty-five joints. In the male several joints are fused into one 

 (see PI. XXII., Figs. 2 and 3), inside which may be seen a power- 

 ful muscle acting on the succeeding joint, and capable of bending 

 It like a hinge for the purpose of clasping the last pair of feet in 

 the female, which are "somewhat modified for this purpose. 



In the latter sex both antennas are alike. The posterior 

 antennae are two-branched. The mandibles, maxillae, and first and 

 second foot-jaws are all developed. To these succeed four pairs 

 of feet, all two-branched, each branch having three joints, except 

 the inner branch of the first pair, which has two only. Another 

 and fifth pair of feet, diff-erently formed from the preceding, com- 

 pletes the number of the Hmbs. The abdomen of the female has 

 three joints, that of the male five, and terminates in two short 

 branches, eacli furnished with five divergent setse, forming a pretty 

 fan. 



In the last joint the cloacal orifice may be seen on the dorsal 

 surface, the intestine extending down thereto (see Fig. 12). On 

 either side below the head may be seen a curious triangular 

 marking (see Fig. 4). A somewhat similar one is found on 

 Daphnia, and is supposed to be the homologue of the green gland 

 m the Cray Fish. The position of the heart is shown in Fig. i, 

 and it may be seen to beat rapidly. I have never been able to 

 observe any blood-corpuscles similar to those observable in 

 Daphnia, and consequently the course of the blood cannot be 

 traced. It is probable, however, from the constant agitation of 

 the mouth-organs, that respiration takes place in their vicinity, 



