618 



SCIENCE. 



[N. S. Vol. I. No. 23. 



infinite number of radii drawn from its 

 center. When we make this assumption, 

 however, we need not necessarily assume 

 that nucleated fragments that will still de- 

 velop into larvse after division of the oos- 

 perm, natural or artificial, must be isotropic. 

 They may be seolotropic from the beginning, 

 but in precisely the same way in each case, 

 as a result of the successive cleavages of the 

 germ-mass, by means of planes that cut each 

 other at right angles, as in the diagram Fig. 

 1, where each of the four segments are pre- 

 cisely alike from the pole a to that of b. 



Fig. 1. 

 The unlikeness of the pole a from 6 is indi- 

 cated by the stippling. This unlikeness 

 would manifestly be unimpaired by segmen- 

 tation of the germ into four quadrants by 

 the first two cleavages, as shown in the dia- 

 gram. The same might hold of octants of 

 the spherical germ. Here the initial seolo- 

 tropy of the whole egg determines that of 

 its segments; that must therefore become 

 four or eight molecular mechanisms, each 

 with precisely the same type of potentiality 

 as that of the whole egg. (See concluding 

 note.) 



There may, according to the foregoing 

 view, be such a thing as perfect isotropj^ in 

 every radius lying in a plane cutting the 

 line from a to 6 at right angles. This would 

 not, however, be the perfect isotropy of our 

 definition that we are compelled to accept 

 in the form in which it comes to us from 

 the physicist. 



As development proceeds, moreover, we 

 have reason to believe that this teolotropy 

 becomes more and more marked, so tha^ 



eventually the huge metameric molecules 

 become arranged in definite linear, parallel 

 systems, as in the axis cj'linders of nervB 

 cells and in muscular tissue. Here the 

 characteristics of the sj^stem become the 

 the same in parallel lines, and in any dh-ec- 

 tions at right angles to an axis parallel to 

 these parallel lines of molecules. That is, 

 in certain rectangular directions there is an 

 approximation toward homogeneitj-. But 

 the completest homogeneity is found to oc- 

 cur in onlj' one direction in parallel lines 

 extending through the mass. This condi- 

 tion we may designate as monotropy. 

 Starting with the extreme geolotropic condi- 

 tion of the germ, we must, therefore, assume 

 that as organization becomes more and 

 more complete, in the progress of develop- 

 ment, in the specialized systems of tissues 

 and organs, the molecules become more and 

 more definitely monotropic. Therefore they 

 at last become incapable, as dj'namical sys- 

 tems, of exhibiting a complex development 

 such as is manifested by a germ, but cap- 

 able only of manifesting the special phys- 

 iological functions entailed by their dyna- 

 mically and mechanicallj' evolved mono- 

 tropism. 



We can now understand why it is that 

 the germinal matter of a species always re- 

 mains in an seolotropic state. Since germ- 

 inal matter is always relieved of specialized 

 functions in the body of the parent, it must 

 perforce remain in its primitive condition of 

 germinal potentialitj' as a molecular mech- 

 anism. Since the germ is material that 

 has been produced in excess of the needs of 

 metabolism of the parent body, as supposed 

 bj' Haeckel and Spencer, it can do no work 

 for that body. The unbroken continuity of 

 the processes of metabolism has provided 

 the conditions for the continuous or inter- 

 rupted production of germinal matter. 



The nearest approach to a condition of 

 continuity of germinal matter is found in 

 the tissue of the ' growing points ' of plants. 



