DEGENERA TION, 



221 



no denial. On any other theory, the existence of gill-arches in the 

 young of an animal which never possesses gills is to be viewed as an 

 inexplicable freak of Nature a dictum which, it is needless to remark, 

 belongs to an era one might well term prescientific, in comparison with 

 the " sweetness and light " of these latter days. 



Hanging very closely on the aphorism respecting development and 

 its meaning, is another biological axiom, wellnigh as important as the 

 former. If development teaches that life has been and still is pro- 

 gressive in its ways, and that the simpler stages in an animal's history 

 represent the conditions of its earliest ancestors, it is a no less stable 

 proposition that at all stages of their growth living beings are subject 

 to the action of outward and inward forces. Every living organism 

 lives under the sway and dominance of forces acting upon it from 

 without, and which it is enabled to modify and to utilize by its own 

 inherent capabilities of action. It is, in fact, the old problem of the 

 living being and its surroundings applied to the newer conceptions 

 of life and nature which modern biology has revealed. The living 

 thing is not a stable unit in its universe, however wide or narrow 

 that sphere may be. On the contrary, it exists in a condition of con- 

 tinual war, if one may so put it, between its own innate powers of life 

 and action, of living and being, and the physical powers and condi- 

 tions outside. This much is now accepted by all scientists. Differ- 

 ences of opinion certainly exist as to the share which the internal con- 

 stitution of the living being plays in the drama of life and progress. 

 It seems, however, most reasonable to conclude that two parties exist 

 to this, as to every other bargain ; and, regarding the animal or plant 

 as plastic in its nature, we may assume such plasticity to be modified 

 on the one hand by outside forces, and on the other by internal actions 

 proper to the organism as a living thing. Examples of such tenden- 

 cies of life are freely scattered everywhere in Nature's domain. For 

 instance, we know of many organisms which have continued from the 

 remotest ages to the present time, without manifest change of form or 

 life, and which appear before us to-day the living counterparts of 

 their fossilized representatives of the chalk, or it may be of Silurian 

 or Cambrian times. The lamp-shells {Terehratida) of the chalk exist 

 in our own seas with wellnigh inajopreciable differences. TheLingula 



