202 



ZOOLOGY. 



insertion of the muscles it 

 stomacli ; it is about twice th 



Fig. 140 —Anatomy of Phascolosoma 

 GoitkliU cut open, with the flaps pinned 

 down, (e, cesophasns ; «/', two short 

 muecles ; p?', two lonj; r tractor mus- 

 cjes; V, next to a dark line the ri^iit 

 Bide of tlie lonij cesopliagus indicating 

 the water-vascnlar tube ; n, nervous 

 cord ; *, eegmental organs ; the long, 

 twisted intestine returns, ending at a 

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

 ley. 



blood-system of the Gephy 



enlarges, but there is no true 

 e 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. Xcar this 

 point is situated a pair of large, 

 long, slightly twisted segmental 

 organs(*)thefree ends of which 

 flare slightly. The nervous, 

 system («) forms an oesophageal 

 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 lyiiig next to the ner- 

 vous oesophageal 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 ^\ ith the di- 

 gestive tract, forming a ruffle- 

 like organ (y), ending at a point 

 nearly opposite the vent {«). 

 Prof. Greef finds that the vas- 

 cular system of Echiunis con- 

 sists of tAvo main vessels, i. e., 

 a dorsal and a ventral vessel ; 

 the former extending along the 

 alimentary canal, and sending 

 a branch to the proljoscis, ^\■her& 

 it divides into two branches, 

 each uniting with the ventral 

 vessel. The blood is pale yel- 

 lowish, with corpuscles. The 

 rca, then, is homologous with 



