127 



Fig. 1. 2 vascular trees from pharyngeal region E. T. = 

 encysted Trematode, diameter 142 mm. 



those described by Oudemans, Bürger and v. Kennel, and the 

 peculiarities were constant in the very large number of specimens 

 . examined. 



In my specimens ^ the vascular prolongations mentioned by v. 

 Kennel as occur- 

 ing in the sucker, 

 arise from the en- 

 tire length of the 

 lateral vessels and 

 also, but to a very 

 much less extent, 

 from the dorsal 

 vessel. They are 

 best developed at 

 the sides of the 

 "pharynx" and 

 gradually dimi- 

 nish towards the sucker. On each side of the "pharynx" there are usu- 

 ally about seven of these "vascular trees" arising from the lateral vessel 



At its origin the trunk of each 

 tree is small and circular, but im- 

 mediately widens, commences to 

 branch , and leads into numerous 

 blindly ending and more or less cir- 

 cular vesicles. Each tree is distinct, 

 has no communication with its 

 neighbour, and usually curves irre- 

 gularly upwards. The structure of 

 the walls of the tree and its vesicles 

 does not differ from that of the or- 

 dinary blood vessels , which has al 

 readybeen described by V. Kennel. 

 There is no trace of valves. When 

 the living animal is compressed 

 between slips of glass each tree is 

 seen to pulsate slowly and rhythmically. The whole tree gradually 

 swells, sucking in the blood corpuscles (which can be clearly seen) from 

 the lateral vessel, then it pauses for a moment and as slowly contracts. 

 12 pulsations per minute were observed in a female of 29 mm. The 

 general course of the blood is backwards in the lateral vessels and for- 



V 



-..L 



Fig. 2. very large vascular tree from 



pharyngeal region; length = .440 mm 



from a specimen length 20 mm. 



3 These included both sexes from a few mm long up to 30 mm. 



