1893.] 1"* [Ryder. 



If motions of hard parts upon each other tend to alter or deform the 

 modeling of the surface in a particular way, as seems to have been the 

 case with teeth, the process is kinetogenetic. If the basal part of the 

 conical surface of a pointed tooth have its enamel organ folded under 

 constraint during growth in a conical matrix into which it expands by 

 growth more rapidly at its basal region than the walls of this matrix ex- 

 pand, the result is partly kinetogenetic and partly statogenetic. 



If the development of a blastoderm be conditioned by surface and in- 

 terfacial tension in such wise as to cause it to conform to the configuration 

 of double curvature of the yolk mass upon which it extends itself, the 

 result is mainly statogenetic. If an embryo be pressed down into the 

 blastoderm as the result of constraint from above during its growth, and 

 the surrounding non-embryonic area is thus caused to be reflected over it 

 more and more as growth of both embryo and blastoderm go on, an 

 amnion is developed. This process is kinetogenetic so far as the growth 

 and reflection of the blastoderm is concerned, but statogenetic in so far 

 as the permanent molding and retention of the figure of the amniotic cavity 

 is concerned. It fin-rays are fractured or segmented in a regular lashion 

 and in response to the exigencies of the motions of the tin, sucli a result 

 is kinetogenetic. If the calcifiable matrix developed about a notochordal 

 axis be regularly segmented at points alternating with the intervals be- 

 tween the myotomes by the agency of the motions to which such an axis 

 is subjected during use, the result is again kinetogenetic. If an originally 

 globular egg be distorted into an ovoidal body withiu a tubular oviduct 

 due to circular pressure, as happens in birds and insects, the result is 

 almost purely statogenetic. An empirical mathematical formula may 

 therefore be written for every variation in the shape of the common hen's 

 egg for a curve which shall account also for its shape. 



If, as in the case of the double monsters developed in meroblastic eggs 

 due to karyokinetic disturbances, there is a strong iuterfacial tensional 

 attraction between the germ and yolk substance, it is impossible to shake 

 the first blastomeres apart as in the case of holoblasiic eggs, so that fused 

 embryos or monsters only can be produced from such meroblastic ova. 

 Such a result is statogenetic, that is, statical conditions in the meroblastic 

 egg so far override the ontogenetic processes that fused monsters only are 

 liere possible, whereas in holoblasiic ova in which the blastomeres can 

 be completely separated two or more distinct embryos can be produced 

 from what had begun its development as a single embryo. 



So universal is this interference of the statical conditions of the plasma 

 of segmenting ova with the ontogenetic processes, that not a single meta- 

 zoan organism can be named the development of which is not thus marred 

 in some way or other. It is often a long time relatively after development 

 has begun that there is any obvious delineation of the embryo. In fact, 

 this cannot take place until the statical energies of surface-tension which 

 have kept the egg globular are overridden. In so far as the ontogeny of 

 any organism is mari-ed by statical conditions of energy-display, its em- 



