Anatomical structure of Aspidogaster conchicola. 509 



bend obliquely downwards and outwards and run forwards in the infra- 

 septal body gradually curving towards one another again after in- 

 closing between them the genital glands. The anterior ends of these 

 tubes do not lie in the sucker as Voeltzkow describes, but for their 

 whole length they lie in the body parenchyma above the limiting 

 membrane of the sucker. Their walls show wavy or crenated con- 

 tractions due to the unextended condition of the body, their muscular 

 contraction, and to the large nuclei bulging into their lumina. In 

 their fluid contents, in some animals, I have seen myriads of bacilli 

 in active motion or clustered on the walls of the vessels, similarly 

 to what Leuckart describes for the medicinal Leech (Parasiten, 

 2. Auflage); while in others were balls and irregularly shaped bodies 

 of difierent sizes from small granules up to structures measuring 

 13 X 23 (.1. The larger also seemed , from their uneven, strongly 

 refracting surfaces , to be made up of smaller elements cemented 

 together and were freely movable or apparently sessile on the inner 

 walls of the vessel whose cavity they filled from its anterior end half 

 way back to its outlet. These I have seen in only two or three cases. 

 They are doubtless to be considered as concretions. Outside of the 

 muscle layer are now and again to be seen small flat cells, lengthened 

 in the direction of the vessel, with stainable protoplasmic contents 

 and nucleus with nucleolus. These seem to be a continuation of the 

 subcuticular cells which persists in great numbers round the posterior 

 ends of the collecting vessels. 



The anterior ends of these vessels project far into the forward 

 prolongation of the foot (to within ^/^o mm of its anterior border) 

 and suddenly narrow to much smaller tubes (Fig. 8, 7) which bend 

 directly back along the collecting vessels for a short distance (as 

 much as Vs iïiïïi) before rising into the neck region. In all former 

 accounts the origin of the smaller out of the end of the larger vessel 

 has been overlooked. The former, it was thought, originated from the 

 dorsal side of the latter, a little distance from its end. From here 

 the tubes turn upwards, on each side of the copulatory organs, into 

 the neck (Fig. 2, 7, 1 Ex). At about the level of the anterior end 

 of the pharynx each bends sharply backwards upon itself so as to 

 form a loop of which both portions are spirally wound except when 

 the neck is fully outstretched. Immediately after the backward turn, 

 or more generally soon after passing the pharynx there appear ciliary 

 organs (Fig. 24) on the inner walls which are present from this 

 onwards till we come to the second last branches. 



34* 



