68 BULLETIN OF THE 



as well as the formation of crystals in solutions, as examples of 

 growth in the inorganic world, he asks : " Is not the growth of an 

 organism a substantially similar process?" and adds : "Around a 

 plant there exist certain elements that are like the elements which 

 form its substance, and its increase in size is effected by continually 

 integrating these surrounding-like elements with itself; nor does 

 the animal fundamentally differ in this respect from the plant or 

 the crystal." 



Now, as opposed to this, I must express my belief that the more 

 we know of the actual details of the process of growth in plants 

 and animals the more clearly it will be seen that this process does 

 differ so fundamentally from that by which a crystal is formed and 

 increases'in size, or from any increase in size of inorganic bodies, that 

 the same scientific term cannot, with any propriety, be applied to 

 both, however long popular usage may have given to both a com- 

 mon name. When inorganic bodies increase in size the additional 

 atoms are deposited on their external surfaces ; or, if a fluid, after 

 penetrating the interstices of some porous body, deposits there any 

 material held in solution, the mass, indeed, is increased thereby, 

 but not the size. When, however, vegetable protoplasm grows, it 

 does not merely integrate with itself certain elements around it like 

 the elements which form its substance ; the needed elements exist 

 in compounds quite unlike itself, aud it combines them together 

 into protoplasm in all parts of its mass, so that it grows by a process 

 of intussusception wholly unlike anything that occurs in the inor- 

 ganic world. In the case of animal protoplasm, the mode of growth 

 by intussusception is the same, but the capability of combining 

 together mere inorganic elements into its own substance is lost ; 

 and, besides these, a certain amount of pre-existing vegetable or ani- 

 mal protoplasm must be present in the food, or growth will not 

 go on. 



In both cases, when the growth has proceeded to a certain extent — 

 within certain definite limits — a new characteristic phenomenon 

 occurs in a growing mass of vegetable or animal protoplasm ; it 

 multiplies by division, its whole mass participating in the act, in 

 accordance with one or other of a few definite methods. This pro- 

 cess is repeated again and again. The progeny may separate, with- 

 out modification, as independent forms, or, as in the case of the 

 more complex organisms, they may cohere together, and the process 

 culminates by groups of them undergoing certain definite and 



