274 A THEORY OF HEREDITY VIII 



by the name " coccoplasma." In the simplest form 

 of plastid, the "cytod," which is devoid of nucleus, 

 and is exhibited by those lowly organisms known as 

 Monera, by the young Gregarina (Ed. van Beneden), 

 by the hyphse of some Fungi, and by the ripe egg of 

 all organisms (if we may judge from the results of the 

 most recent researches), coccoplasm and protoj)lasm 

 are not differentiated, but exist as one substance, 

 which Haeckel, following Ed. van Beneden, distin- 

 guishes as ''plasson." Whether these distinctions 

 have a real value or not, is of no moment for the 

 question in hand. It is a widely-accepted doctrine — 

 in fact, the fundamental generalisation on which 

 Biology as a science rests — that the excessively com- 

 plex chemical compound which forms the substance 

 of plastids or life-units is the ultimate seat of those 

 phenomena or manifestations of energy which distin- 

 guish living from lifeless things — to wit, growth by 

 intus-susception, reproduction, adaptation, and con- 

 tinuity or hereditary transmission. Leaving Professor 

 Haeckel's pamphlet for a time, let us go back thirteen 

 years. 



As long ago as July 1863, Mr. Herbert Spencer, 

 in his Principles of Biology, pointed out at consider- 

 able length (vol. i. p. 181) that the assumption of 

 definite forms, and the power of repair exhibited by 

 organisms, is only to be brought into relation with 

 other facts (that is to say, so far explained) by the 

 assumption that certain units composing the living 

 substance or protoplasm of cells possess " polarity " 

 similar to, but not identical with, that of the units 



