203 



ZOOLOGY. 



insertion of the muscles it enlarges, but there is no true 

 stomach ; it is about twice the length of the body, and is bent 



and twisted on itself, ending 

 dorsally in a vent marked by an 

 external wart, on the anterior 

 third of the body. Near this 

 point is situated a pair of large, 

 long, slightly twisted segmcntal 

 organs(s)the free ends of which 

 flare slightly. The nervous, 

 system (n) forms an cesophageal 

 ring, and from it passes a well- 

 marked ventral single cord, 

 from which at short intervals-, 

 pass off small short lateral 

 nerves. The vascular system 

 is represented by a circular 

 vessel lying next to the ner- 

 vous cesophageal ring, sending, 

 branches into, or at least in 

 communication with, the cavi- 

 ties of the tentacles, and from 

 the ring passing along and in- 

 timately connected with the di- 

 gestive tract, forming a ruffle- 

 like organ (v), ending at a point- 

 nearly opposite the vent (a). 

 Prof. Grcef finds that the vas- 

 cular system of Echiurus con- 

 sists of two main vessels, i. e., 

 a dorsal and a ventral vessel; 



Fig. 140 -Anatomy of Pkascolo^na the f ormcr extending along the 



GonMii, cut open, with the flaps pinned alimentary canal, and sending 



down, a, oesophagus ; a>\ two short 



muscles ; ;;/, two long r tractor mus- a branch to tllC proboSCIS, where 



cles; , next to a dark line the right .... , . 



Bide of the long oesophagus indicating it divides into two branches, 



the water-vascular tube ; , nervous . ... . , , 



cord ; s, seginentnl organs ; the long, Cadi Ullltlllg With the VClltraL 



twi-ted intestine returns, ending at a i mi vi i i i 



Natural size. Drawn by J. S. Kings- VBSSel. 1 he blOOU IS pale yel- 



lowish, with corpuscles. The 

 blood-system of the Gephyrea, then, is homologous with 



