334 STUDIES IN GENERAL PHYSIOLOGY 



cell-membrane, and that it certainly has no relation to the 

 orientation of the first cleavage plane. For when we first 

 allow the eggs to develop in ordinary sea-water into the two- 

 cell stage before bringing them into dilute sea-water, it can 

 be noticed that the first cleavage plane may lie in any posi- 

 tion with regard to the point of rup- 

 ture; the material lying nearest the 

 rupture will be that which flows out. 

 Figs. 91-94 are drawings of eggs 

 the membranes of which were made 

 to rupture in the two-cell stage, and 

 which illustrate what has been said 

 more clearly than words. Since the 



extraovate develops in all cases, if it is only sufficiently large, 

 we must conclude that, so far as the question of divisibility 

 is concerned, the protoplasm must be considered an isotropic 

 substance. 



9. What conceptions can we form of the nature of the 

 smallest elements of living matter which are capable of 

 development? As Nussbaum has shown, every attempt that 

 has been made of assuming as the ulti- 

 mate elements of living matter some- 

 thing analogous to the atom and the 

 molecule has failed, for the simple rea- 

 son that two different substances, nucleus 

 and protoplasm, are necessary. One 

 might assume that a combination of two 

 different "micellae "-one composed of 

 nuclear material, the other of proto- FIG - 92 



plasm might represent the smallest living element. Our 

 experiments show that such an idea would be entirely wrong, 

 when full capacity for development is taken as the criterion 

 of living matter, inasmuch as a very considerable quantity 

 of substance is necessary for full development an amount 



