160 



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 segmental 

 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 O3sophageal 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 (-), ending at a point 

 nearly opposite the vent (). 

 Prof. Greef finds that the vas- 

 cular system of Echiurus con- 

 sists of two main vessels, i. e. } 

 a dorsal and a ventral vessel ; 



Pig. no.-Ana7omy of Phatcoiosoma the former extending along the 

 alimentary canal, and sending 



eles ; v, next to a dark line the right . - ... . r 



side of the long (Esophagus indicating it divides into two branches, 

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



cord ; s, segmental organs ; the long, each Uniting With the VClltral 

 twisted intestine returns, ending at a T 



Natural size. Drawn by J. S. Kings- VCSSel. 



ley 



m, n > - , -, 



The blood IS pale Vel- 



lowish, with corpuscles. The 

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



