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XIII. 
VARIATION: GERMINAL AND ENVIRONMENTAL. 
By J. C. EWART, M.D., FBS. 
Regius Professor of Natural History in the University of Edinburgh. 
[ CommunicaTED By Proressor D. J. Cunnincuam, M.D., F.R.S., Vicz-Presipent, Roy. Dusrin Socrery. | 
(Reap Marcr 20, 1901.) 
Introductory. 
ALL are agreed that variability is intimately associated with changes in the 
protoplasm out of which animals and plants are made, but there is not yet 
universal agreement as to the causes of these changes. It may, however, be 
taken for granted that protoplasm has varied to produce recent and extinct 
organisms, either (1) because it was at the outset endowed with inherent internal 
attributes, or (2) because it has from the first been susceptible to the influence of 
external forces. 
A century and a half ago certain naturalists (the extreme ‘‘ preformationists ” 
or ‘‘ evolutionists”) believed in the theory of encasement, or emboitement, which 
not only implied that each ovum contained a complete fully formed embryo, 
but that each embryo contained ova for the next generation, these ova, other 
ova in their turn, and so on ad injfinitum—KEKve, for example, ‘‘ encasing” all her 
descendants, each complete but necessarily infinitely minute. 
The ‘‘preformationists” of the middle of last century—for a time championed 
by Bonnet—may be said to be now represented by neo-preformationists with 
Nigeli as their most scientific apologist. The main difference between the extreme 
old and extreme new “evolutionists” is, that the latter are, if anything, more 
thorough going, some of them believing that the protoplasm originally introduced 
was pre-ordained, or especially endowed with the power to give rise to a countless 
number of plants and animals quite uncontrolled by external stimuli—the external 
forces at the most playing a subordinate role, modifying or improving, but never 
interfering with or determining the line of development. Though it is not alleged 
that the original protoplasm contained miniatures of all the plants and animals 
TRANS, ROY. DUB. SOC., N.S VOL. VII., PART XIII. 3 D 
