No. 520] BASIS OF MEN DELI A N PHENOMENA 



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changes in metabolism between nucleus and cytoplasm, 

 but from the unity of the cell, which modern biology has 

 abundantly proved. Hence there is no difficulty in sup- 

 posing that differences which must be thought of as 

 characterizing the germ cell as a whole, originated from 

 chromosomal differences during reduction. On the other 

 hand, there seems no necessity for assuming that all 

 germinal differences originate in the chromosomes, 

 although if they originated in the cytoplasm it is neces- 

 sary to assume as a vera causa either a separation of 

 cytoplasmic substances during reduction, of which we 

 have no visible evidence, and which seems unlikely for 

 various reasons, or quantitative cytoplasmic differences 

 in the cells of a tetrad. The quantitative difference 

 which must exist between the germ cells of 0. rubricalyx 

 and 0. rubrinervis may possibly be conceived of as origi- 

 nating in the cytoplasm and then becoming a property 

 of the germ cell as a whole. 



It is even possible that this is not a difference in 

 amount of matter of any sort, but rather in the energy 

 content of the two types of germ cell, although 

 have no means of knowing how or why such a mark 

 difference in energy-content should arise. 



To attempt to account for the manner of origin of 

 0. rubricalyx mutant from a 0. rubrinervis germ c: 

 would at the present time be purely speculation. De- 

 Vries' conception of a new unit becoming suddenly acti- 

 vated in the germ plasm seems too formal an assumption 

 to be accorded the dignity of an explanation. The fact 

 that the 0. rubricalyx mutant reverts to 0. rubrinervis 

 may be looked upon as evidence in favor of his vie. 



of a mutated with a non-mutated germ cell. 



T should also point out that the origin of 0. rubricalyx 

 from 0. rubrinervis may perhaps be significant as indi- 

 cating an orthogenetie tendency to an increase of pig- 

 ment production, although this increase lias taken place 

 by definite germinal steps, particularly in the origin o 

 0. rubricalyx from 0. rubrinervis. 



