a. = 
overe we 
ADDRESS, Ixxili 
This instance (a knowledge of which is due chiefly to the researches of 
Von Siebold) I have thought it requisite to quote, in order to convey some 
idea to my non-physiological auditors of the singular complexity of powers 
and arrangements tending to the ultimate right lodgement and well-being of 
a seemingly insignificant noxious little parasite. 
The sum of the recent researches on the generation of the Entozoa teaches 
that to the success in life of the majority of these internal parasites, two 
different species of much higher organized animals are subservient ; and that 
these two species stand in the relation of prey and devourer. 
The habits of the prey favour the accidental introduction (as when a slug 
crawls over the droppings of a thrush) of the eggs of the birds’ intestinal 
parasite. These are hatched in the slug. The slug in its turn is devoured 
by the thrush; but the parasitic passengers are not digested—only the coach 
is dissolved, and the larvez, thus set free, find in the warm intestines of the 
bird the appropriate conditions for their metamorphosis and full develop- 
ment. 
In like manner, the Rhynchobothria of a cuttle-fish are the larve ‘of the 
Tetrarhynchus or four-tentacled tape-worm of a dog-fish. The encysted 
sexless Zrienophorus of the liver of the char becomes the free and perfect 
Trienophorus of the gut of the pike. The Ligula of a herring becomes a 
Tenia only when introduced into the interior of a cormorant. The bladder- 
worm (Cysticercus fasciolaris) of the mouse’s liver becomes the tape-worm 
(Tenia crassicollis) of the cat. The Cysticercus pisiformis of the liver of 
the hare becomes the Tenia serrata of the dog and fox. 
Dr. Kiichenmeister of Zittau first proved, experimentally, by feeding 
animals with Cysticerci (Hydatids of the flesh and glands of herbivorous 
animals), that they became Zenie (intestinal tape-worms) in carnivorous 
animals. The results of these instructive experiments were published in 
1851*. They have been successfully repeated, amplified, and scientifically 
explained, in regard to every particular and step of the progress, by the 
indefatigable and accurate Von Siebold+. The part which Parthenogenesis 
plays in the changing scenes of entozoal life is acutely discerned and clearly 
explained in this work. 
Since the time when it was first discovered that plants and animals 
could propagate in two ways, and that the individual developed from 
the bud might produce a seed or egg, from which also an individual 
might spring capable of again budding,—since this alternating mode of 
generation was observed, as by Chamisso and Sars, in cases where the 
budding individual differed much in form from the egg-laying one—the 
subject has been systematized{, generalized, with an attempt to explain its 
* Gunsburg’s Zeitschrift fiir Klinische Vortrige, 1851, p. 240. 
+ Ueber die Band- und Blasenwirmer, &c. 8vo. Leipzig, 1854. 
} Steenstrup (J.), “‘ Ueber den Generationswechsel oder die Fortpflanzung durch abwech- 
selnde Generation,” Kopenh. 1842. 8vo. 
