228 Dr. F. E. Beddard on the Genus Tiicliodiilus. 



tion of the living worms, as well as upon sections througli 

 the body of preserved individuals. 



When living this species of Trichodrilus was remarkable 

 for its very active movements if touched. It is a slender 

 worm of rather under an inch to perhaps an inch and a half 

 in length, perhaps even longer. Its diameter is only half a 

 millimetre. The red blood-vessels are conspicuous, but the 

 thick covering of chloragogen cells upon the intestine renders 

 it difficult to study in the living condition under low powers 

 of the microscope. 



Certain characters can, however, be ascertained by such an 

 examination. The colour, when the worm is seen in reflected 

 light, is a golden yellow, from which the bright red main 

 trunks of the vascular system stand out. Clapar^de mentions 

 yellow as the colour of the only species of the genus described 

 by him "^j viz. Trichodrilus allohrogum. I do not think that 

 this colour is due to pigment, but rather to a reflection of the 

 effect of the chloragogen covering of the intestine. In any 

 case it is very conspicuous, but disappears when the worm is 

 viewed under the microscope with transmitted light. 



The 2^^'ostomiurn is long, rather more than twice the length 

 of the lirst segment of the body j it is bluntly pointed. It 

 agrees fairly well with the figure given by Claparbde f. I 

 did not find any tactile processes standing out from the surface 

 of the prostomium, such as occur in Phreatothrix and are 

 referred to by Vejdovsky and myself; but it may be that 

 these processes had disappeared or been withdrawn when the 

 worms had been for some time in a dish and were, perhaps, 

 commencing to die. 



The setcB are strictly paired, slender and delicate, with 

 simply pointed free extremity — in fact, precisely like those of 

 the individuals examined by Clapar^de. It was very rarely 

 that I observed " s^■oies de reuiplacement.''^ I could detect no 

 differences in character or size between dorsal and ventral 

 set?e or between those of different segments. 



Vascular System. — So far there is no reason to believe that 

 the specimens of Trichodrilus sent to me from Norfolk differ 

 from Clajiar^de's species, T. allobrogum, found in Switzerland. 

 But an inspection of the trunks of the vascular system does 

 show differences, and those of some importance. Claparfede 

 fiirures branches of the dorsal vessel, of which there are five 

 or, occasionally, six in the posterior segments of the body. 



* " Reclierclies Anatomiques sur les Oligocbetes," Mem. Soc. Phjs. et 

 Hist. Nat. Geneve, t. xvi. pt. 2 (1802). 

 t Loc. cit. pi. iii. lig. 15. 



