_ ENTOMOSTRACA OF MINNESOTA. 127 
plate, above and between the stylets. No special divarications or ceca 
are appended to the digestive tract, 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 crustacz, 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 impossble to 
find this organ in Canthocamptus, in every case, it being very obscure; 
and its office is uncertain, though it is supposed, perhaps 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 
office of a pulsating heart, though in a very imperfect manner. 
There are no true hematic 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 
derived 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 vas- 
cular system should surround the alimentary canal is no unexampled 
thing, for in Daphnia a large sinus embraces a portion of the canal. 
The same provision as this described in Canthocamptus occurs in the 
Oyclopide. The nutritive globules are often very large, and are fre- 
quently 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 commis- 
sures around the cesophagus, 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 cannot locate with certainty 
the organs of any sense. There are, however, two spots which are 
evidently devoted to special sense: first, the processes on the fourth 
joint of the antenne, which may be simply the seats of tactile sense, 
or may have nerves suitable for perceiving chemical stimuli; second, 
the area on the forehead bordered by a raised line and covered with 
little pits, each with a small bristle. The character of this organ can 
be but conjectured; it may be homologized with the frontal nervous 
organs of the Cladocera. 
