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KATHLEEN HADDON. 
profound morphological change during which all the larval 
organs vanish, and the testes together with their efferent 
ducts are formed. Owing to this transformation Hansen 
states that the morphological orientation of the adult is 
uncertain. As, however, the larva is attached by its 
anterior end, it seems unlikely that the developing male 
would revolve round in its larval skin, so as to reverse its 
anterior and posterior ends, hence it is in all pi'obability safe 
to speak of the openings as occurring at the anterior end of 
the male. 
The loss of the alimentary canal is also interesting, 
especially as it has practically gone in the female as well, 
thougli in this case its place is taken by the absorptive root 
system. The male seems to be without the means for 
obtaining nourishment. 
IV. Relation op Parasite to Host. 
The most frequent position of the female Herpyllobius 
is on the head of the worm, although it is sometimes 
attached to a parapodium. Levinsen (9) describes the root 
system of the parasite as forming a tongue-shaped body lying 
by the side of the gut of the host, and I have been able to 
confirm this statement by means of sections. In the worm 
sectioned the parasite was attached to the head, and the roots 
actually pierced through the cerebral ganglion of the host 
(PI. 22, fig. 8) to reach the alimentary canal, and further on 
(PI. 22, fig. 9) could be seen lying by the side of the oesophagus, 
which had been pushed over to one side by this intrusion. 
The internal economy of the worm with three parasites on its 
head must have been extremely deranged, but unfortunately 
it did not cut well and I was unable to make out the relative 
positions of the three roots. 
The roots obviously have an absorptive function, and 
the process must be carried on in spite of the protective 
envelope formed by the worm round it. The lacunar tissue 
of the root system is in continuation through the stalk with 
