THE CHARACTERISTICS OF ORGANISMS 19 



till they form a breakwater a thousand miles long; the Arctic 

 jellyfish {Cyanea arctica) becoming bigger and bigger till the disc 

 is over seven feet in diameter and the tentacles trail in the waves 

 for over a hundred feet. Again, many an animal egg-cell develops 

 into a body that weighs billions of times as much as its beginning; 

 and this is far exceeded in the growing up of giants — like a Blue 

 Whale, eighty-five feet in length, or an Atlantosaurus with a thigh- 

 bone as high as a tall man. 



Multiplication. — ^The corollary of growth is multiplication, a 

 term that we are using here in preference to the more general word 

 reproduction, which includes the whole series of functions con- 

 cerned with giving rise to other organisms. Multiplication essen- 

 tially means separating off portions or buds, spores or germ-cells, 

 which start a new generation. In the asexual method of separating 

 off large pieces, the connection with growth is obvious; multipli- 

 cation occurs as a consequence of instabilities which follow over- 

 growth. As Haeckel said long ago, reproduction is discontinuous 

 growth. Its externally simplest form is seen in the division of an 

 overgrown imicellular organism, yet in the everyday division of 

 most of the cells of plants and animals, this has been elaborated 

 into an intricate process, which secures that each of the two 

 daughter-cells gets a meticulously precise half of everything that 

 is in the parent-cell. 



The connection between growth and cell-division is not far to 

 seek. Spencer, Leuckart, and James pointed out independently that 

 as a cell of regular shape increases in volume, it does not propor- 

 tionately increase in surface. If it be a sphere, the volume of cell- 

 substance or cytoplasm to be kept alive increases as the cube of 

 the radius, while the surface, through which the keeping alive is 

 effected, by various processes of diffusion, increases only as the 

 square. Thus there tends to set in a hazardous disproportion 

 between volume and surface, and this may set up instability. The 

 disturbed balance is normally restored by the cell dividing into 

 two cells. R. Hertwig has pointed out that the nucleus is a dynamic, 

 perhaps trophic, centre to the cell, and that stability depends on 

 keeping up a certain proportion or relation (Kernplasma-Relation) 

 between the nucleoplasm and the cytoplasm. Here again a con- 

 nection between growth and division is indicated, for if the growth 

 implies an increase of cell-substance out of proportion to nuclear 

 substance, a state of physiological instability may set in, which 

 cell-division may counteract. It is not inconsistent with this that 

 some large cells, like muscle-cells and big Protozoa, become multi- 

 nucleate ; and it may be that some cytoplasmic complications like 

 chromidia (see the chapter on the Cell) may be arrangements for 

 increasing nuclear influence outside the nucleus. The details of 

 ordinary cell-division are in appearance very intricate, but it may 



