383 
W. Nicoll 
fasciatus) which they considered to be the larva either of Hymenolepis murina 
or of some yet unrecognized species. Such a species has now been discovered 
by Baylis (1922) and named Hymenolepis longior. 
Of some interest is the record by Parisot and Joyeux (1920) and Blanc 
and Caminopetros (1921) of the discovery of the larvae of two tapeworms of 
the cat (Dipylidium trinchesei and D. chyzeri). 
In contrast to the meagre amount of work on Cestode life-history is the 
large volume of interesting researches on Nematode larval development. 
Most prominent amongst this is Looss’s monograph on the life-history of the 
hookworm. This work, however, is now so generally known and has been so 
extensively reviewed and commented upon that no further criticism appears 
necessary. One point nevertheless, of some importance has arisen, namely the 
alleged heterogenesis or alternating life-cycle of Ancylostoma. Surprising as it 
may seem to anyone with a working acquaintance with hookworm develop¬ 
ment this point has been raised anew by more than one observer but in view 
of the very large consensus of confirmation of Looss’s work it is to be hoped 
that the matter has been finally settled. 
Of more recent date is the work of Faure-Fremiet on the embryological 
development of Ascaris. Extending over a number of years this work was 
published in the form of a large monograph in 1913. 
The most important work on Nematode life-history is, possibly, that on 
the life-history of Ascaris, investigations which probably rank next in import¬ 
ance to those on Bilharzia. The names most closely associated with this work 
are those of Stewart, Ransom, Foster and Yoshida. Stewart, experimenting 
with rats and mice, found that the infecting larvae pursued a migratory course 
in the body of the experimental animal somewhat similar to that followed 
by the larvae of Ancylostoma, namely a passage through the intestinal wall, 
transference to the lungs via the blood stream and a migration thence via the 
trachea into the intestine again. The fact that these larvae, after they had 
again reached the intestine, did not develope further there but were passed 
out with the intestinal contents led Stewart at first to form the hypothesis 
(abandoned later) that rats and mice constituted a sort of intermediate host 
for the Ascarids. (It may be noted that no species of adult Ascaris has ever 
been recorded as a natural parasite of rats or mice.) This view was not accepted 
by Ransom and Foster (1919) who have demonstrated that a similar migratory 
course is pursued by larval Ascarids in infecting their natural host, e.g. Ascaris 
lumbricoidcs in the pig. It is thus evident that there is some resemblance 
between the invading stages of Ascaris and Ancxjlostoma , the essential point 
of difference in the life-history, however, being that Ascaris has no external 
free larval life. 
In addition to his work on the life-history of Ascaris Ransom has added 
considerably to our knowledge of the life-history of two other Nematode 
j P aras ites, namely Habronema muscae and Gongylonema scutatum , both of 
which are of decided importance in veterinary helminthology. In the case of 
25—2 
