1887.] 



ON CYCLESTHERIA HISLOPI. 



29 



at the end on either side to a very short and broadly rounded 

 cæcum, quite simple, without any trace of folds or lobes, and 

 communicating with the intestinal cavity by a wide opening 

 (see fig*. 3. c). Of any true liver, similar to that found in 

 all other known forms of the present group of Phyllopoda, not 

 the slightest trace can be detected, and in this respect the 

 present Phyllopod occupies even a still lower rank than the 

 Branchipodidæ, in which the cæca are found to be at least 

 more or less distinctly folded or lobed. The structure of the 

 intestinal tube is that usually met with, its walls being rather 

 thin and surrounded by numerous circular muscles. At the end 

 of the trunk the intestine terminates with a well-defined rectum, 

 traversing the caudal part close to its ventral side, and opening 

 at its extremity between the two caudal claws. The latter part 

 of the intestinal canal is very strongly muscular and generally 

 devoid of contents, except when at intervals the excreménts are 

 «xpelled from the anal orifice. 



c. The Circnlatory System. 



The heart, located as usual in the dorsal part of the bod} 7 

 immediately posterior to the cephalic division, is very easily ob- 

 served in living specimens through the transparent shell (see Pl. 

 H, Pl. III, fig. 1, Pl. VII, fig. 7, h, Pl. VIII, figs. 1, 4). In its struc- 

 ture, it would seem to be rather different from that of Estheria, 

 in which latter genus it has been described as constituting a 

 very short sac-like organ with but a single pair of lateral open- 

 ings and extending scarcely beyond the first segment of the 

 trunk. On the other hand, this organ in the present form agrees, 

 I find, precisely with that in Limnadia lenticular is, as ex- 

 amined by myself in Norwegian specimens of that Phyllopod. 

 As in the latter Phyllopod, it has the form of rather an elongate 

 tube traversing no less than 4 segments of the body, viz., the 

 maxillary segment and the three first segments of the trunk, its 

 posterior part being, moreover, extended to the middle of the 

 succeeding segment and its anterior extremity slightly projected 



