20 Henriksen, A Functional view of Development. 



tionaJ activity. i. e., the ability to form a protoplasm strueture 

 siniilar to that which has been broken down by the katabolic action 

 or it differentiates it to form, at last, an organism similar to that 

 of the parent. 



With this as a basis I shall endeavor to show that the theory 

 of the strueture of germ-plasm by our highly esteemed zoologist, 

 Weismann, is unnecessary and when brought out in details is quite 

 absurd, and that we have no right to claim that the egg is some 

 kind of a microcosm of the ontogeny and a shortened recapitulation 

 of the phylogeny of the organism into which it develops. I shall 

 endeavor to show that from the facts known we have no reason 

 to believe the embryo is predelineated nor even singly prede- 

 termined but all we can say is that the egg possesses the ability 

 of forming the proper relations in the first cleavage so that the 

 development, if undisturbed, may go toward establishing what 1 

 have called the equilibrium of the species, and that this equilibrium 

 is peculiar to each species and even if disturbed it tends towards 

 re-establishing it. But let us first try to define equilibrium used 

 in this way. 



The equilibrium of the species is that which determines the 

 developing organism to grow into an organism much like that of 

 the parents. It is the result of the relations in the egg, blastomere, 

 etc., and this depends primarily on its inherited functonol ability ; 

 secondarily, on proper environment and proper nutrition. The 

 fertilization of the egg disturbs this equilibrium within the egg 

 and causes the cleavages, and this process goes on, establishing 

 proper relations between the cells resulting in the produetion of 

 the adult organism. Among the cells of the body it is caused by 

 nutrition and the factors in the environment, as I will show later. 

 It must be clear to every student of the phenomena of development 

 that physiological relations are not broken by cell division, as I 

 will also show later; that in many forms their position alone 

 determines their destination; and that the prime factor of the ner- 

 vous System is to establish these relations in the more highly 

 organized animals. 



The relations are the physiological interactions among the 

 cells, or among the parts of the cell; in fact the latter is the all 

 determining factor for establishing the relations between the bla- 

 stomeres and thus in a progressive manner the organism reaches 

 to a state of equilibrium peculiar to that of the species. That 

 these relations may easily be disturbed and new relations estab- 

 lished towards the equilibrium of the species we shall proeeed to 

 show, but let it first be kept clear in mind that they are by no 

 means mechanical only, but that every fact of embryology shows 

 them to be of a much deeper nature. The earlier cleavages of 

 the gastropods, polyclades and annelids show wonderful similarity 

 in forming three quartets of micromeres. If the relations were 

 mechanical they should form similar struetures in all of these 

 animals but as we know such is not the case. They are peculiar 



