108 
HALF HOURS WITH INSECTS. 
[Packard. 
But it is generally and correctly thought that sex is deter¬ 
mined at the time of conception. Now in the Aphis embryo, 
at a stage long before even the rudiments of feet appear, 
Metznikoff figures certain cells which are destined to form 
eggs, and soon after the germ has acquired limbs a mass of 
these eggs may be plainly seen. So the egg is to our eyes 
feminine almost as soon as it begins to grow. 
It is interesting to watch the finishing strokes Nature puts 
to her master pieces. Shortly before hatching, the embryo, 
so far as regards the mouth-parts, resembles that of a fly or 
beetle or bee nearly as much as a bug ; and it is to be remem¬ 
bered that the beak of the Aphis is really a very complex 
affair. It is composed of jaws (mandibles) and the front 
pair of maxillae, which form two pairs of bristle-like organs 
ensheathed within the labium or under lip (second maxillae). 
MetznikofFs figures show us how this wonderful transforma¬ 
tion of parts takes place. How the mandibles and first max¬ 
illae suffer an arrest of development, while the second pair 
of maxillae are greatly enlarged and joined together to form 
the so-called labium or under lip, until finally the parts as¬ 
sume the beak-like form of the mature insect. 
Thus from the simplest of beginnings the most complex 
results follow. “Give me a point on which to rest my lever,” 
said Archimedes, “ and I will lift the world.” “Give me a 
drop of protoplasm,” says the biologist, “and I will con¬ 
struct the world of animals and plants.” Let us remember 
that all animals, as well as plants (except one-celled ones), 
result from the subdivision of a single primitive cell, and 
that, simple as this process is, yet mystery upon mystery 
accompanies each process. What is the power that urges on 
the self division of cells, that arranges them into forms so 
varied as the world presents ? Is life a function of proto¬ 
plasm ? What is the difference between these sacs of pro¬ 
toplasm, that one becomes a plant, another a monad, another 
a fish, and another, to speak in the concrete, a Shakspeare 
12 
