. Biology. Biology. FIG. 76.—Centrolecithal type of egg and cleavage in the crayfish. The nuclei, after several divisions, pass to the periphery of the egg after which radial cleavage planes divide it into cells. (From Parker and Haswell.) of the body, and compares with the lateral organs of fishes or the semi-circular canals of vertebrates. 4. The Eyes--The eyes of arthropods are entirely different from those of higher groups of animals. Vision is compound, the eyes being made up of thousands of minute units, termed ommatididj each ommatidium having a complex structure (Fig. 75). The facets (
. Biology. Biology. FIG. 76.—Centrolecithal type of egg and cleavage in the crayfish. The nuclei, after several divisions, pass to the periphery of the egg after which radial cleavage planes divide it into cells. (From Parker and Haswell.) of the body, and compares with the lateral organs of fishes or the semi-circular canals of vertebrates. 4. The Eyes--The eyes of arthropods are entirely different from those of higher groups of animals. Vision is compound, the eyes being made up of thousands of minute units, termed ommatididj each ommatidium having a complex structure (Fig. 75). The facets (cornea), like mosaics, form the outer cuticle of the eye. REPRODUCTIVE -The sexes are separate in the ma- jority of Crustacea, and the gonads are relatively much larger than in the earthworm. The testes are long, beaded organs, white in color, lying dorsally to the hepato-pancreas, one on each side of the dorsal blood system. The male gonoduct or vas deferens originates about two-thirds of the length from the anterior end, and runs downward through the body cavity to. 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 Calkins, Gary N. (Gary Nathan), b. 1869. New York, H. Holt and company
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