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 regaixls 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 verj- complex 

 aff'air. It is composed of jaws (mandibles) and the front 

 pair of m.axillaj, which form two pairs of bristle-like organs 

 ensheathed within the labium or under lip (second maxillifi). 

 INIctznikoff's figures show us how this wonderful transforma- 

 tion of parts takes place. How the mandibles and first max- 

 illae suff"er 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 tlie 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," sa3-s 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-ceiled 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 



