EDITORIAL OBSERVATIONS. 121 
guished helminthologists for an explanation of the nature, 
structure, and habits of the sheep fluke, but they have not, 
as far as I am aware, ever suggested any remedial measures. 
Dr. Cobbold admits that this description of the genetic rela¬ 
tions of the parasite may, on further researches, require some 
modification in its minor details, yet asserts positively (and 
my own observations confirm his assertion) that in the main 
his general description will be found substantially correct. 
It will be necessary for my purpose to set forth briefly, and 
in the plainest terms I can use, Dr. Cobbold's explanation of 
the phenomena of fluke life. It is as follows : Fluke is 
especially prevalent during the spring months, at which 
season of the year large quantities of fluke eggs, and some¬ 
times probably living flukes themselves, escape from the 
infested animal, through the common duct of the liver into 
the intestinal canal, and thence are transferred with the 
dung to the pasture grounds. The eggs thus freed are very 
minute, not measuring more than the I60th part of an inch 
in diameter; they are furnished with a lid at one end of the 
shell, for the facility of the escape of the ciliated or hairy - 
edged embryo, each containing only a single germ, to be 
subsequently developed by a process analogous to plant¬ 
budding. The action of the dew, rain, or pools of water on 
this egg, assisted by the vital movements of the embryo 
contained within, serve to loosen the lid of the shell, and 
the animalcule is thus set free. The liberated animalcule, 
which at this stage is less than the 160th part of an inch in 
diameter, as soon as convenient, after its release finds and 
attaches itself to the body of a small snail or mollusc, 
always abundant in wet sour-grass country; it then parts 
with its hairy covering, and gains access to the interior of its 
friend. Once there, the embryo disappears, leaving the 
germ-bud, which now undergoes a rapid development, and 
being bisexual, begins already to reproduce itself by a second 
progeny formed within its own interior. It is then trans¬ 
formed into a sac or cyst for .the support and protection of 
its contained progeny, and in this condition is called a 
nurse.” These nurse-progeny are furnished with tails, and 
when fully developed are the well-known cercarise. The 
cercarise now migrate from the bodies of their host, and for 
