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396 Address of Professor Huxley. 
rise to offspring which run through the same cycle as them- 
selves, but also others, producing offspring which are of a total- 
ly different character from themselves, the researches of two 
centuries have led to a different result. That the grubs found 
in galls are no product of the plants on which the galls grow, 
but are the result of the introduction of the eggs of insects into 
the substance of these plants, was made out by Vallisnieri, 
Reaumur, and others, before the end of the first half of the 
eighteenth century. The tapeworms, bladderworms, and flukes 
continued to be a stronghold of the advocates of Xenogenesis 
for a much longer period. Indeed, it is only within the last 
thirty years that the splendid patience of Von Siebold, Van 
Beneden, Leuckart, Kiichenmeister, and other helminthologists, 
familiar experience to eve tt. that mere pressure on the skin 
will give rise to acorn. Now t 
morphologically di: e from the parasite worm, the 
_ of which is neither more nor less closely bound up with that of 
the infested organism. bo | 
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