. Elements of comparative zoology. Zoology. ACERATA 231 in the ocean itself. None of them nave any economic importance aside from their acting as scavengers and serv- ing as food for fishes. Class II.—ACERATA. In these arthropods the body is divided into two regions a cephalothorax in front and an abdomen behind. The cephalothorax bears the eyes (of which there may be sev- eral pairs) and six pairs of appendages, none of which can be considered as antennae. The abdomen may have or may be without apparent appendages. The respira- tory organs are confined to the abdomen, and in their development
. Elements of comparative zoology. Zoology. ACERATA 231 in the ocean itself. None of them nave any economic importance aside from their acting as scavengers and serv- ing as food for fishes. Class II.—ACERATA. In these arthropods the body is divided into two regions a cephalothorax in front and an abdomen behind. The cephalothorax bears the eyes (of which there may be sev- eral pairs) and six pairs of appendages, none of which can be considered as antennae. The abdomen may have or may be without apparent appendages. The respira- tory organs are confined to the abdomen, and in their development are always connected with the abdominal limbs. They may be of three kinds: (1) External gills borne on the abdominal legs; (2) internal sacs (lungs) with numerous leaf-like folds; (3) air-tubes or tracheae, strikingly like those of the Insecta, but with a different history. The reproductive organs open near the middle of the body. Subclass I.—Merostomata. Here belong the horseshoe crabs (fig. 59) of our east coast (and a number of fossil forms), which breathe by means of leaf-like gills; which have both simple and compound eyes, and which have the bases of the walking-feet of the cephalo- thorax modified to serve as jaws. Recent investigations show that the horseshoe crabs are not related to the true crabs, but are to be rather closely associated with the —Horseshoe crab (LimU" lus polyphemus).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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