. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Cephalo-thoracic par- 766 ganglia, strictly speaking, are united into a single mass of a greatly elon- gated form, and presenting a little way back, like the fourth ganglion of the Palemon, a cleft for the trans- mission of the sternal artery. The transition Fig. 394. from the Deca- vv // . poda Macroura to the Brachyura takes place by the Homola, and certain Anomou- ra,* in which the constantly in- creasing concen- \// tration of the thoracic nervous centres coincides with the almost rudimentary state of the abdominal g
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. Cephalo-thoracic par- 766 ganglia, strictly speaking, are united into a single mass of a greatly elon- gated form, and presenting a little way back, like the fourth ganglion of the Palemon, a cleft for the trans- mission of the sternal artery. The transition Fig. 394. from the Deca- vv // . poda Macroura to the Brachyura takes place by the Homola, and certain Anomou- ra,* in which the constantly in- creasing concen- \// tration of the thoracic nervous centres coincides with the almost rudimentary state of the abdominal ganglionic sys- tem, which is here reduced to a kind of median trunk without en- largements. This, too, is .ejwu-noracu! par-the disposition tion of the wemms Presented by the system of tlie Pali- nervous system nurus Vulgaris. in the Carcinus mosnas among the Brachyura, with this difference only, that the medullary nuclei are rather closer to one another, and more intimately The tho- racic ganglion has the form of a ring, the cir- cumference of which gives origin to the nerves of the thoracic appendages. The single abdomi- nal cord is in its rudimentary state, in obvious relation with the abdomen itself, and therefore reduced to very insignificant dimensions. It is in the Maja,J in fine (Jig. 395), that the nervous system is found in its highest degree of centralization; for the elements"of which the two masses there encountered are composed, are so intimately conjoined, that no trace can be found of their ever having existed indepen- dently, although among neighbouring geneia several of them may still be discovered isolated- ly. The cephalic ganglion («) is a sufficiently faithful counterpart of that of the Lobster. The nervous cords (g) which connect this first portion of the system with the thoracic portion also present the same arrangement as in the Lob- ster ; there are similar mandibular nerves, a like gastric pair, the same transverse band (g') behind
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