VIL. 
Experimental Embryology.’ 
XPERIMENTAL Embryology is the youngest department of 
biological science; for although the idea of artificially in- 
fluencing the germ is very old, and although even Swammerdam 
is said to have experimented in producing monstrosities, all the 
important results are very recent. They are already so important, 
both in themselves and in their suggestiveness, that it is imperative 
on every biologist to take stock of them. In part this has been already 
done by Weismann in his recent book on ‘‘ The Germ Plasm,” and 
by Roux, in an address delivered to the congress of the Auatomische 
Gesellschaft, held last June in Vienna; but already there are further 
researches of moment to be taken account of, and a fresh survey may 
be permitted. A critical review I do not propose to attempt, partly 
because that may be more profitably left to the expert embryologists, 
partly because it may be conveniently deferred until the body of facts 
has had time to become integrated. 
I. Just as pathology sheds light on physiology—for instance, in the 
case of the thyroid gland—so teratology may help us to understand 
normal development. The most successful worker along this line 
has been M. Camille Dareste. He is the acknowledged chief of 
artificial teratologists. To attempt an appreciation of his results 
would lead us far into morphological questions ; suffice it to say that 
he has experimented with the eggs of birds, placing them vertically 
instead of horizontally, hermetically varnishing part of the shell, 
keeping them slightly above or slightly below the normal temperature 
of incubation, heating different parts of the egg unequally, and so on. 
He has not only shown that the germ is plastic in the grip of its 
environment, he has been able to induce various malformations 
which are of interest to the student of morphology. 
Dr. Bertram C. A. Windle, Professor of Anatomy in the Queen’s 
College, Birmingham, has followed up some of Dareste’s investiga- 
tions, observing on the eggs of the fowl the effect of (a) excluding 
part of the air supply by varnish, (b) incubating under electrical 
current, and (c) incubating in the proximity of magnets. He is very 
cautious in his conclusions. He confirms, however, the view of 
Dareste that the same anomalies may be produced by diverse 
1 A Paper read before the Scottish Microscopical Society, March ro, 1893. 
