276 T, R, LEWIS. 
worm might contribute many thousands of ova; or the worm, 
after depositing its ova, may have taken its departure, or 
have died and become disintegrated. The scarred and saccu- 
lated condition of the aorta, already described, which is some- 
times observed unassociated with any parasite at the time of 
the examination, shows that the worm that produced the 
lesion may altogether disappear. 
Moreover, we require to know far more than is at present 
known concerning the development and parentage of these 
canine microscopic blood-worms, before anything definite can 
be stated with reference to their relationship to similar 
organisms found in the blood of dogs in France, China, 
Japan, and America. 
So far as I am aware, Dr. Spencer Cobbold is the only 
author who has suggested that the young of the Filarie 
sanguinolente may possibly find their way into the blood'— 
a suggestion which is the more noteworthy, seeing that, to 
the best of my knowledge, no observations had been recorded 
showing that this nematode ever penetrated the arteries. 
Although I have not been able to keep individual dogs 
affected with this heematozoon during any lengthened period, 
still there can hardly be any doubt but that, as has already 
been shown with reference to the human heematozoon and 
been previously remarked concerning heematozoa in animals 
generally,” these microscopic worms may exist for a consider- 
able time in the blood (unaltered after having attained a 
certain, very imperfect stage of development), showing that 
they were not in the place or fluid fitted for their growth. 
Their presence in the blood, it may therefore be presumed, 
is accidental, or if not exactly accidental, the young brood 
requires at least to be transferred to some other habitat before 
undergoing even the most elementary morphological changes. 
When, however, the ova or liberated embryos of the 
Filaria sanguinolenta find their way into a ‘ host’ or other 
medium suitable for their development they enter the larval 
stage—a stage in their development carried on, possibly, to 
the extent of providing the embryo with some kind of oral 
armature and a differentiated intestinal tube. Having ac- 
quired this stage of growth, the further progress of the 
parasite is probably dependent on its being swallowed by 
some such animal as the dog, to the mucous lining of whose 
cesophagus it attaches itself, then penetrating the muscular 
'¢Entozoa: an introduction to the study of Helminthology,’ London, 
1864, p. 95. Supplement to ditto, p. 63. 
* In dogs in France and China; in the frog, and in the crow.—-Leuckart. 
