The Development of the Individual and Its Heritable Tendency

Abstract

The lapse between just-fertilized egg-cell and fully grown and mature individual, from a developmental point of view an enormous one, is fraught with all kinds of possibilities. On the one hand the gene complex (present in the fertilized nucleus) and on the other hand, the surrounding plasm. This plasm is perhaps partly independent and partly cooperating as a re action substrate for the genes in order to establish the phenotype. Both components are influenced in their attempt to express themselves, that is to say, they are favoured or inhibited by external circumstances of life, (i.e., by the environment). By means of cooperation of these three groups of causes, thrown together in each others company, the body of the organism originates as a unit, as a living creature and a differentiated complex of cells. If genetics is to answer the problems to it, then we have firstly to exclude the effect of difference in environment, as far as is possible. In this way we are able to derive some conclusions from our experiments which may be due to interaction of genes and plasm. This however will entail very great difficulties.