ACTIVATION OF UNFERTILIZED STARFISH EGGS. 293 



of this preliminary treatment is seen in the fact that an after- 

 exposure of only 4 minutes was sufficient to induce development 

 to larval stages in more than half of the eggs. After-exposure 

 to butyric acid solution has the same favorable effect when the 

 preliminary warming is sufficient to form membranes in all eggs ; 

 in a second similar series on September 12 the eggs were exposed 

 for 4 minutes to 32° and all mature eggs thus treated formed 

 membranes ; without any after-treatment almost none (less than 

 I per cent, formed larvae, but with an after-treatment of 4 to 8 

 minutes with n/260 butyric acid favorable development took 

 place in a large proportion of eggs. 



General Discussion and Conclusion. 

 The interchangeability of the treatments with warm sea-water 

 and butyric acid solution indicates that both agents produce 

 their effect by inducing the same kind of change in the egg- 

 system. This change is evidently of a "releasing" kind, and 

 initiates the sequence of developmental processes; these, once 

 started, continue automatically to their conclusion. Probably 

 their most distinctive peculiarity is the highly specific character 

 of the chemical transformations that take place. From the food 

 contained as reserves in the egg, or taken in from the surround- 

 ings, the developing germ builds up the specific compounds 

 which form the structural basis of the organism; this synthetic 

 process, in the case of the chief structure-making compounds, the 

 proteins, undoubtedly starts — as in the constructive metabolism 

 of the adult animal — with the amino-acids, which are recombined 

 in the specific manner predetermined by the chemical organiza- 

 tion of the germ. Bodies of the most highly specific and indi- 

 vidualized physical and chemical properties are thus built up 

 and laid down in definite positions as development proceeds. 

 Their properties and their spacial disposition determine at any 

 time the character of the transformation undergone by the 

 building material which is being incorporated. According to 

 this conception it is the chemical specificity of these substances 

 that determines the specific character of development in the 

 more evident or morphological sense, ^ i. e., why the egg gives 



1 Reichert's work on the crystal-forms of haemoglobin and other complex 

 compounds from different species of animals and plants constitutes perhaps the 



