. A manual of zoology. Zoology. 434 ARTIIliOPODA. being united behind, while their ducts remain separate. The structure of the nervous system is in part dependent upon that of the abdomen. In the Macrura (fig. 430, C) the ventral chain consists of six ganglia in the thorax, six in the abdomen, but in the Brachyura (fig. 441) these all flow together in a common mass, connected with the brain by two long esophageal commissures. The development of most decapods is interesting from the number of larval forms. As a rule a zoea (fig. 415) is hatched from the egg ; this passes next into a Mysis-stage
. A manual of zoology. Zoology. 434 ARTIIliOPODA. being united behind, while their ducts remain separate. The structure of the nervous system is in part dependent upon that of the abdomen. In the Macrura (fig. 430, C) the ventral chain consists of six ganglia in the thorax, six in the abdomen, but in the Brachyura (fig. 441) these all flow together in a common mass, connected with the brain by two long esophageal commissures. The development of most decapods is interesting from the number of larval forms. As a rule a zoea (fig. 415) is hatched from the egg ; this passes next into a Mysis-stage (fig. 443) in which head, thorax, and abdo- men are distinct, the thorax bearing biramous feet like those of schizo- pods—a proof of the origin of the simple feet from the biramous type. In the crabs (Brachyura) the Mysis-stage is replaced by a Megalops (fig. 443), in which the abdomen is well developed but the feet have lost their. 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1902
