. Outlines of zoology. Zoology. 256 CRUSTACEA. deeply pigmented. Thus each element consists of corneal facet, crystalline cone, and retinula, and the retinula consists of internal rhabdome, and external retinula cells. Between the individual optic elements lie some pigment cells. The eyes are able to form images of external objects, and these images are erect, not inverted as in the eyes of Vertebrates. Alimentary system.—The food canal consists of three distinct parts, a fore-gut or stomodseum developed by an intucking from the anterior end of the embryo, a hind-gut. Fig. 107.—Longitudinal se
. Outlines of zoology. Zoology. 256 CRUSTACEA. deeply pigmented. Thus each element consists of corneal facet, crystalline cone, and retinula, and the retinula consists of internal rhabdome, and external retinula cells. Between the individual optic elements lie some pigment cells. The eyes are able to form images of external objects, and these images are erect, not inverted as in the eyes of Vertebrates. Alimentary system.—The food canal consists of three distinct parts, a fore-gut or stomodseum developed by an intucking from the anterior end of the embryo, a hind-gut. Fig. 107.—Longitudinal section of lobster, showing some of the organs. H., Heart ; AO., ophthalmic artery ; aa., antennary artery; ah., . hepatic artery; ST., sternal artery; SA., superior abdominal artery; MG., mid-gut; DG., digestive gland ; HG., hind-gut; Ex., extensor muscles of the tail; FL, flexor muscles of the tail; I A., inferior abdominal artery; G., gizzard; C, cerebral ganglia; P., pericardium ; T., testes. or proctodaeum similarly invaginated from the posterior end, and a mid-gut or mesenteron, which represents the original cavity of the gastrula. The mouth has been shunted backwards from the anterior end of the body, so that the antennules and antennae lie far in front of it. The fore-gut, which is lined by a chitinous cuticle, includes a short " guilet," on the walls of which there are small glands, hypothetically called "salivary," and a capacious gizzard, which is distinctly divided into two 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 Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
