THE ANNELIDES OE ENTOMOZOARIA. 



367 



by a double chain of communicating 

 filaments occupying the median line 

 of the body near its ventral aspect (Fig. 

 139). In most of the inferior arti- 

 culated animals, and in the more 

 elevated, but whose development 

 is not finished, these ganglions are 

 almost all equal, and form, thus con- 

 nected together, two chains resem- 

 bling knotted cords from one end of the 

 body to the other (Fig. 336) ; but, as 

 we ascend in the scale, we find a dis- 

 position in these ganglions to a fusion, 

 in the lateral and longitudinal sense 

 (Fig. 337), so as to form a mass. In 

 crabs, this centralization is carried 

 so far as to form but two nervous 

 masses for all the rings or segments 

 of the body, one situated in the 

 head, the other in the thorax ; but 

 even in this case the nervous collar 

 encircling the gullet is always found, 

 so that two such masses seem the 

 maximum of nervous fusion. In the 

 mollusca we also find the nervous 

 collar; but the ventral or post-ceso- 

 phageal ganglionary portion is com- 

 posed in them only of one or two pairs 

 of ganglions situated on the median 

 line of the body ; whilst in the anne- 

 lides we find a long series of ventral 

 ganglions ; and when we find in this 

 part of the body merely a single 



Fig. 336. Anatomy 

 of the Sphinx.* 



* Sphinx of the privet : a, cephalic ganglions, or brain, situated before the 

 gullet, and giving origin to the optic nerves, &c. ; b, nervous cords of com- 

 munication, connecting the first pair of ganglions with the second, and in 

 their course encircling the gullet ; c, first pair of post-o3sophageal ganglions 

 situated behind the mouth ; d, ganglions of the first ring, or segment of the 

 thorax ; e, nervous mass formed by the ganglions of the second and third 

 thoracic rings ; f, sixth pair of abdominal ganglions ; h, the mouth ; i, the 

 proboscis ; j, the gullet ; k, the stomach ; /, the intestine and biliary vessels ; 

 m, large intestine ; H, the anus ; o, feet of the first pair ; p, feet of the second 

 pair ; q, feet of the third pair ; r, first pair of membranous feet of the larva ; 

 , dorsal vessel ; t, first ring of the thorax ; u, horn surmounting the extre- 

 mity of the abdomen in the larva. 



