444 SCIENCE PROGRESS 



changes may in exceptional cases so alter the whole mechanism 

 that this effect is not produced." 



It must always be remembered that the chromosomes and 

 the cytoplasm are in intimate connection, and that the latter 

 may exert modifying influences on the former. This may be 

 illustrated by another analogy of Doncaster's "If in the 

 hydrocarbon CHgH the fourth hydrogen atom is replaced 

 by chlorine (CH3CI) or by hydroxy 1 (CH3OH), substances of 

 very different properties are produced. The cytoplasm, in 

 this analogy, is represented by the hydrocarbon radicle C Hg— 

 and the effects on the general nature of the resulting compound 

 of substituting - CI or— OH for the — H of the hydrocarbon 

 represents the effect produced by substituting a chromosome 

 ' bearing * one factor for a chromosome bearing another." 



A parallel series could be CgHgH, CgHgOH. C2H5CI. The 

 hydrocarbon radicle (cytoplasm of the analogy) is not negligible 

 since C H3CI differs considerably from C2H5CI ; but it is true to 

 say that the substitution of a hydrogen atom by an hydroxyl 

 radicle turns hydrocarbon into an alcohol : and in the same way 

 the replacement or addition of a chromosome may considerably 

 alter an egg's potentialities. 



The cytological aspect of Artificial Parthenogenesis will be 

 considered in a future article ; but this somewhat long intro- 

 duction is necessary to make clear many of the problems raised 

 by a consideration of the results obtained in this field of 

 research. 



