i] CHEMICAL EMBRYOLOGY 21 



of soul which is suitable for his need in its preparing for itself its 

 peculiarly fit dwelling-place by means of the matter implanted in 

 the maternal body, for we do not suppose it possible that the soul is 

 adapted to a strange building, just as it is not possible that a certain 

 seal should agree with a different impression made in wax". 



Thus the soul makes its body as if it were a gem making a stamp 

 upon some soft substance, and acting during embryogeny from 

 within — a conception essentially like that of Driesch. We shall see 

 later how many Renaissance authors adopted similar views, e.g. 

 Fienus. "No unsouled thing", says Gregory, "has the power to 

 move and to grow. Yet there is no doubt that the embryo moves 

 and waxes big as it is fed in the body of the mother." There is nothing 

 new about dynamic teleology; it is by no means the outcome of 

 newly ascertained facts : it recurs from time to time in the history of 

 biological thought because it is the natural result of an unscientific 

 attitude. 



I do not propose to discuss here the facts which originally led 

 Driesch to the views expressed in his Science and Philosophy of the 

 Organism, for they are very well known, and have been shown by 

 J. W. Jenkinson, H. S. Jennings, H. C. Warren and A. E. Boveri, 

 among others, to be interpretable on quite other lines. Nor shall I 

 demonstrate by a comparison of passages from Driesch and Paracelsus 

 how closely the conception of immanent formative force or entelechy 

 approaches the master-archaeus of Paracelsus and the later iatro- 

 chemists such as Stahl, for Driesch has done it himself in his History 

 and Theory of Vitalism. The inference from it is that the Drieschian 

 entelechy has been and will be of no more use as a practical working 

 hypothesis for the laboratory than the archaeus was in the past. 



Driesch's dynamic teleology is open to more serious and funda- 

 mental objections. These were not obvious at the first appearance 

 of his Gifford Lectures, but were clearly brought to light through 

 the controversy which Jacques Loeb had with H. S. Jennings and 

 which resulted in the publication of their respective books, Forced 

 Movements, Tropisms, and Animal Conduct and The Behaviour of the Lower 

 Organisms. Loeb's theory of tropisms entirely dispensed with any 

 psychological factors, but Jennings upheld the view that they might 

 be legitimately brought under scientific discussion, provided they 

 were regarded as being determined as well as determining. This led 

 him to make a new enquiry into scientific methodology, and he 



