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economy, but whether it is workable or non-workable, efficient or 
inefficient, is mainly a physical property of the type itself. The same 
is true of the more restricted germinal cycle (in relation to its somatic 
environment). We know very little, it is true, about the proximate 
factors in germinal equilibrium which must be maintained in the 
succession of cell-divisions 1 along the germ-track, if a new germ-cell 
is to be produced. But we may presume that it implies a certain 
co-ordination of physiological reactions between the various complex 
proteins, lipoids, nucleic acids, etc., of the chromosomes and the 
cytoplasm of the cell. The germ-cell has its own particular type of 
physiological economy, and any variation in this type must conform 
in the first place to the necessities of germinal equilibrium. Whether 
such a variation is initiated by external or internal factors, it must 
be conceived primarily as a co-ordinated readjustment of these 
various reactions, and not as a mechanical rearrangement of some 
structural complex. That such spontaneous changes are possible may 
be presumed from an analogy with the similar readjustments that 
frequently occur in somatic life. Germinal variations must indeed 
be regarded as a kind of functional adaptation in the germinal cycle 2 . 
A successful variation must however not only conform to the 
necessities of germinal equilibrium, it must also result in a stable 
and efficient soma. We have already discussed some of the proximate 
factors in somatic equilibrium, which are extremely specialised and 
intricately co-ordinated in many of the higher organisms. Many of 
them are so elaborate that a serious modification of any single factor 
(for example the chemical composition of the duodenal hormones, 
the function of the erythrocytes, or the character of the neural 
linkages that form the presumptive bases of the primary instincts) 
would require a profound alteration in the whole economy of the 
organism if equilibrium were to be maintained. 
If, therefore, as the mutationists suppose, the germinal and 
somatic cycles are functionally independent, is there any justification 
for assuming that a germinal readjustment conditioned only by the 
equilibrium requirements of the germinal cycle would also conform 
to the necessities of somatic equilibrium? There is no reason for 
such an assumption, for the types of physiological economy which 
1 Including of course the meiotic divisions which usually occur at or near 
the end of the germinal cycle except in the case of haploid plants. 
2 This view is quite consistent with the discontinuous character of somatic 
morphological changes, and we believe not inconsistent with the quantitative 
aspect of these phenomena revealed by the experimental study of bisexual 
inheritance. 
