THE PERCH 55 
in most spendthrift fashion, creating living organisms whereof 
not one in a hundred, it may be not one in a thousand, have 
the most infinitesimal prospect of attaining maturity. At 
other times she treats the vital principle as a rare treasure, 
hedging the embryo with elaborate defence, and providing 
infinite protection for the young creature. The same want 
of principle, as we may call it in a Pickwickian sense, is 
apparent in all living things, animal and vegetable. The end 
is everything ; the means indifferent. Thus the oak produces 
comparatively few acorns, each enclosed in a horny sheath to 
protect it from injury; while the fig-tree contains in each 
single fruit more living seeds than are borne by a large oak. 
Mammals which undergo long and laborious gestation are 
endowed either with high intelligence to provide for their 
offspring, as is the case with man, or with formidable strength, 
like the elephant. In no class of animals are these extremes 
more manifest than in fish. The sharks and rays, fish of a 
very primitive type which existed many ages before the modern 
bony fishes which we are considering had been evolved, lay 
few and large eggs. Some species may possibly be vivi- 
parous, that is, their young are produced alive, thereby 
escaping all the perils incident to eggs and tender alevins 
abandoned to chance; but most of the sharks produce a few 
—very few—eggs, each of which is enclosed in a large purse 
or sheath of an exceedingly tough, horny substance. When 
the young creature is ready for a start in life, this case 
splits along one of its ends, and a little shark, dog-fish, or 
ray, already several inches long, swims abroad upon a career 
of destruction. 
The cod, on the other hand, affords an instance of the 
opposite extreme. Ai single large female may deposit as many 
as nine million eggs, every one of which is the germ of 
a potential twenty-pounder. Yet neither sharks nor cod 
increase perceptibly in numbers. By severe economy of the 
principle of life in one case, by reckless disdain for it on the 
