ON PHYSIOLOGICAL MORPHOLOGY. 



53 



Figs. 23 and 24 represent double Plutei and Fig. 25 a triple 

 Pluteus. 



It is remarkable that the development of these monstrosities 

 goes on nearly at the same rate as that of the normal embryo, 

 provided they are equally well 

 supplied with oxygen and 

 equally protected from mi- 

 crobes and infusoria. If pre- 

 formed germ-regions deter- 

 mined the arrangements of 

 organs in the embryo, we 

 ought to expect that these 

 ruptured ova would give rise 

 to single embryos, with a 

 modified arrangement of 

 limbs, and not to several 

 embryos with normally ar- 

 ranged limbs. Nevertheless, 

 it remains true that the de- 

 velopment in most eggs takes 

 place in such a regular and 

 typical manner that it seems as if there were a pre-arrangement 

 of some kind. But it is perfectly well possible that this pre- 

 arrangement consists in a separation of different liquid sub- 

 stances in the ovum by the molecular qualities of these 

 liquids. Such a separation, of course, might be called a 

 preformation of germ-regions, but it would be something 

 totally different from what is now understood by that term. 



FIG. 23. 



V. THEORETICAL REMARKS. 



i. All life phenomena are determined by chemical processes. 

 This is equally the case whether we have to do with the 

 contraction of a muscle, with the process of secretion or with 

 the formation of an embryo or a single organ. One of the 

 steps that physiological morphology has to take is to show in 

 every case the connecting link between the chemical processes 

 and the formation of organs. I have tried to show that in a 



