TRANSACTIONS OF SECTION D. 833 
food, it commonly happens that these stages are passed through in a very 
modified form, the embryo being as in a four-day chick, in a condition in which it 
is clearly incapable of independent existence. 
The nutrition of the embryo prior to hatching is most usually effected by 
granules of nutrient matter, known as food yolk, and embedded in the protoplasm 
of the egg itself; and it is on the relative abundance of these granules that the 
size of the egg chiefly depends. 
Large size of eggs implies diminution of number of the eggs, and hence of the 
offspring ; and it can be well understood that while some species derive advantage 
in the struggle for existence by producing the maximum number of young, to 
others it is of greater importance that the young on hatching should be of consider- 
able size and strength, and able to begin the world on their own account. In other 
words, some animals may gain by producing a large number of small eggs, others 
by preaneing a smaller number of eggs of larger size—z.e., provided with more 
food yolk. 
The immediate effect of a large amount of food yolk is to mechanically retard 
the processes of development ; the ultimate result is to greatly shorten the time 
occupied by development. This apparent paradox is readily explained. A small 
egg, such as that of Amphioxus, starts its development rapidly, and in about 
eighteen hours gives rise to a free swimming larva, capable of independent exist- 
ence, with a digestive cavity and nervous system already formed; while a large 
egg, like that of the hen, hampered by the great mass of food yolk by which it is 
distended, has, in the same time, made but very slight progress. 
From this time, however, other considerations begin to tell. Amphioxus has 
been able to make this rapid start owing to its relative freedom from food yolk. 
This freedom now becomes a retarding influence, for the larva, containing within 
itself but a very scanty supply of nutriment, must devote much of its energies to 
hunting for, and to digesting, its food, and hence its further development will 
proceed more slowly. 
The chick embryo, on the other hand, has an abundant supply of food in the 
egg itself; it has no occasion to spend time searching for food, but can devote its 
whole energies to the further stages of its development. Hence, except in the 
earliest stages, the chick develops more rapidly than Amphioxus, and attains 
its adult form in a much shorter time. 
The tendency of abundant food yolk to lead to shortening or abbreviation of 
the ancestral history, and even to the entire omission of important stages, is well 
known. The embryo of forms well provided with yolk takes short cuts in its 
development, jumps from branch to branch of its genealogical tree, instead of 
climbing steadily upwards. 
Thus the little West Indian frog, Hylodes, produces eggs which contain a 
larger amount of food yolk than those of the common English frog. The young 
Hylodes is consequently enabled to pass through the tadpole stage before hatching, 
to attain the form of a frog before leaving the egg; and the tadpole stage is only 
imperfectly recapitulated, the formation of gills, for instance, being entirely omitted. 
The influence of food yolk on the development of animals is closely analogous. 
to that of capital in human undertakings. A new industry, for example that of 
pen-making, has often been started by a man working by hand and alone, making 
and selling his own wares; if he succeed in the struggle for existence, it soon 
becomes necessary for him to call in others to assist him, and to subdivide the work; 
hand labour is soon superseded by machines, involving further differentiation of 
labour ; the earlier machines are replaced by more perfect and more costly ones ; 
factories are built, agents engaged, and, in the end, a whole army of workpeople 
employed. In later times a man commencing business with very limited means. 
will start at the same level as the original founder, and will have to work his way 
upwards through much the same stages, 7.¢., will repeat the pedigree of the industry. 
The capitalist, on the other hand, is enabled, like Hylodes, to omit these earlier stages, 
and, after a brief period of incubation, to start business with large factories equipped 
with the most recent appliances, and with a complete staff of workpeople, z.e,, to 
' spring into existence fully fledged. 
