EXPERIMENTAL MORPHOLOGY 333 



ment, giving rise, even when isolated, to definite organs 

 of the embryo. Wilson concluded that the cytoplasm of 

 the egg contains a number of specific organ-forming stuffs, 

 which have a definite topographical arrangement in the 

 egg. Development is thus due in part to a qualitative 

 division not of the nucleus but of the cytoplasm. Corrobo- 

 rative evidence of the existence of cytoplasmic organ- 

 forming stuffs has been supplied for several other species, 

 e.g., Patella (Wilson), Cynthia (Conklin), Cerebratulus (Zeleny), 

 and Echinus (Boveri). 



It is interesting to recall that so long ago as 1874 W. His x 

 put forward the theory that there exist in the blastoderm 

 and even in the egg prelocalised areas, which contain the 

 formative material for each organ of the embryo, and from 

 which the embryo is developed by a simple process of 

 unequal growth. 



The experimental study of form was prosecuted in many 

 other directions besides that of experimental embryology. 

 The study of regeneration and of regulatory processes 

 attracted many workers, among whom may be mentioned 

 T. H. Morgan, C. M. Child, and H. Driesch. In an interesting 

 series of papers C. Herbst applied the principles of the 

 physiology of stimulus to the interpretation of development. 2 

 The formative power of function was studied in Germany by 

 Roux and his pupils, Fuld, O. Levy, Schepelmann and 

 others, particularly by E. Babak. In France, F. Houssay 

 inaugurated 3 an important series of memoirs by himself and 

 his pupils on " dynamical morphology," the most important 

 memoir being his own valuable discussion of the functional 

 significance of form in fishes. 4 The principles of his 

 dynamical morphology were first laid down in his book 

 La Forme ct la Vie ( 1 900). 



The famous experiments of Loeb, Delage and others on 



1 Uftsere Kbr-perform, p. 19, Leipzig, 1874. 



2 Biolog. Centrlbl., xiv., 1894, xv., 1895. Formative Reize in der 

 thicrischen Ontogenese, Leipzig, 1901. 



3 " La Morphologic dynamique," No. i. of the Collection tie Mor- 

 pJiologie dynamiqitc, Paris, 1911. 



4 " Forme, Puissance et Stabilite des Poissons," No. iv. of the 

 Collection, Paris, 1912, 



