166 TWELFTH ANNUAL RIPORT. 



adaptation becomes a sort of force-pump, which, durlug life, is con- 

 stantly pumping water in and out, serving as a means of respira- 

 tion. This anal respiration is quite common among aquatic ani- 

 mals in this as well as other orders. This latter section of the canal 

 is the rectum, and opens beneath a toothed anal plate, above and 

 between the stylets. No special divarications or caeca are append- 

 ed to the digestive traat, and the only other organ which is at all 

 considered to belong to the alimentary system, is what is known as 

 the "shell-gland," present in most Crustacea, but till recently 

 thought to be absent in Canthocamptus. It is a coiled tube found 

 in the lower part of the first segment of the thorax. It is impos- 

 sible to find this organ in Canthocamptus, in every case, it being 

 very obscure; and its oflice is uncertain, though it is supposed, per- 

 haps with little reason, to be hepatic in function. 



There is no functional heart in this animal, but its place is taken 

 by a peculiar apparatus, hitherto undescribed ; this consists of a 

 tube, surrounding the posterior portion of the alimentary canal. 

 This sac around a sac is open in front, and serves by a double 

 mechanism the ofSce of a pulsating heart, though in a very imper- 

 fect manner. 



There are no true haematic or lymph corpuscles in this animal ;. 

 so far, at least, none have been discovered. The place of these 

 blood corpuscles is taken by globules of yellowish or red color of 

 the most diverse size. These nutritive globules, or fat globules, as 

 they have been called, are undoubtedly reservoirs of nutriment in a 

 shape convenient for the animal's use, and equally certainly are 

 deiived from the contents of the intestine. In those Copepoda 

 which have a functional heart, it is open anteriorly into a general 

 body-cavity in the same way as in this animal. That a portion of 

 the vascular system should surround the alimentary canal, is no 

 unexampled thing, for in Daphnia a large sinus embraces a por- 

 tion of the canal. The same provision as this described in Cantho- 

 camptus occurs in the Cyclopidse. The nutritive globules are often 

 very large, and are frequently extremely abundant, especially in 

 females soon to become gravid. Three-hundredths mm. is not a 

 large measurement for the diameter of such drops. 



The nervous system is very hard to trace, consisting of a large 

 pear-shaped ganglion just below the eye, from which extend 

 commissures around the oesophagus, connecting them with the 

 ventral ganglia lying between the bases of the feet. The senses 

 are not apparently well developed, for, excepting the eyes, we can- 

 not locate with certainty the organs of any sense. There are, 



