. A manual of zoology. Zoology. IV. INSECTA: HEXAPODA 409 is the gizzard {hn, pv),ox provenlricidus, the chitinous linirg of which is toothed for grinding the food. The true stomach, of entodermal origin {m, cd), freciuently bears blind sacs or gastric caca (ap); in general it is short and its junction with the hinder ectodermal portion, the proctodeum, is marked by the entrance of the Malpighian tubules (vm). The latter, ex- cretory in function, arise from the proctodeal region. The proctodeum is usually differentiated into a small intestine and a two-regional (colon and rectum) large intesti
. A manual of zoology. Zoology. IV. INSECTA: HEXAPODA 409 is the gizzard {hn, pv),ox provenlricidus, the chitinous linirg of which is toothed for grinding the food. The true stomach, of entodermal origin {m, cd), freciuently bears blind sacs or gastric caca (ap); in general it is short and its junction with the hinder ectodermal portion, the proctodeum, is marked by the entrance of the Malpighian tubules (vm). The latter, ex- cretory in function, arise from the proctodeal region. The proctodeum is usually differentiated into a small intestine and a two-regional (colon and rectum) large intestine. The rectum may have enlargements called rectal glands. True glands, however, occur only at the beginning and end of the alimentary tract; from two to four salivary glands {sp) empty into the mouth; at the anus are defensive anal glands wdth malodorous secretions of a protective character. The alimentary tract with the other viscera is enveloped in the fat body, a soft mass which con- tains, besides fat cells and connective tissue, concretions of uric acid. The nervous system (fig. 370) has the ventral cord, especially in primiti\'e forms (Apterygota, Archiptera, Ortho- ptera, fig. 449), and nearly all larvie (fig. 60), long and composed of numerous separate pairs of ganglia. In beetles, moths, bees (fig. 452), and flies the cord is shortened and the ganglia are in part fused. The brain arises by the fusion of three pairs of ganglia (proto-, deuto-, and tritocerebrum), and is, especially in colonial species, very complex. It is connected on either side with a large optic ganglion, the size of which is cor- related to that of the eyes. In the adult condition the Hexapoda have a single pair of highly developed compound eyes (fig. 372), (each occasionally divided into two), which not infrequently occupy nearly the whole of the top of the head. Between and in front of these, small and simple ocelli, usually three in number, frequently occur, especially in insects which are stron
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
