176 C. M. CHILD. 



direction of incident light is apparently wholly fortuitous, the 

 hereditary mechanism, as expressed in the constitution and pat- 

 tern of the egg protoplasm, determines the occurrence and the 

 nature of the reaction to incident light. In other words the hered- 

 itary constitution of the Fucus egg as well as the direction of 

 incident light is a factor in the determination of the polarity. 

 There is, in short, no conflict between this physiological concep- 

 tion of the origin of organismic or of axiate pattern and concep- 

 tions of heredity. The origin and development of organismic 

 pattern in nature is simply the realization of certain hereditary 

 potentialities of a particular protoplasm in a particular environ- 

 mental complex, which may itself be determined in large meas- 

 ure or wholly by the hereditary mechanism of the protoplasm 

 concerned. 



Surface-interior Pattern and Axiate Pattern. In the light of 

 the conclusions reached concerning the nature and origin of 

 axiate pattern, the question of cell pattern, touched upon above 

 (pp. 150-151) requires some further consideration. It was sug- 

 gested that the cell is primarily a surface-interior pattern result- 

 ing from exposure of the surface of a mass of protoplasm to the 

 action of external factors. Such an exposure is a differential 

 exposure as regards surface and interior. Both the respiratory 

 exchange and excitation can occur only through the surface, 

 therefore differences must arise between surface and interior, 

 and a more or less definite gradient in such conditions from the 

 surface inward must result. As different organs are localized at 

 different levels of an axial gradient so the localization and differ- 

 entiation of the nucleus in the first instance may have resulted 

 from the conditions in the interior of the protoplasmic mass. In 

 fact, it is difficult to see how the nucleus as a definite organ could 

 have arisen otherwise. The differences between nucleus and 

 cytoplasm as regards acidity and electric potential as well as the 

 behavior of nuclei in such specialized cells as spermatozoa, where 

 cytoplasm is practically absent, all suggest that the nucleus is 

 fundamentally an internal cell organ, and if the origin of cell 

 pattern has any relation to environmental factors, the differentia- 

 tion of the nucleus must have been determined originally by con- 

 ditions in the interior of a protoplasmic mass. The fact that the 



