The Origin and Transformation of Animals. 99 



woman comes nearer to that of the man, but without reaching 

 so high a limit." 



From transformation we pass naturally to metamorphosis, 

 and we find that the larva of an insect or crustacean may be 

 regarded as an embryo with an independent life, which obtains 

 its own food instead of being nourished by its mother, and which 

 undergoes before our eyes transformations analogous to those 

 which the young of viviparous creatures experience inside the 

 maternal organism. A proximate cause of metamorphosis may 

 be found in the small amount of organizable material supplied 

 by the yolk of the eggs of creatures which exhibit its peculiar 

 phenomena. In common language, the more imperfect the 

 condition in which the egg turns out its inhabitant, the more 

 extensive the changes which the creature must afterwards 

 undergo. M. Quatrefages observes that, compared with the 

 eggs of certain molluscs, those of insects are enormous. Thus, 

 the egg of the Cossus ligni'perda, which Mr. Noel Humphreys 

 discoursed of in our last number, is about " thirty thousand 

 times bigger than the egg of a teredo." We cannot therefore 

 be surprised that from the former there emerges a caterpillar 

 or animal of a complicated construction, while the ovum of the 

 teredo yields only a simple creature, ' c a homogeneous pulp, in 

 which a digestive tube is vaguely discerned. The first has to 

 fabricate certain organs, but its chief work is to develope and 

 and modify those which it possesses, while the last has every- 

 thing to acquire." In contemplating the changes which we 

 can observe in the lower vertebrates or molluscs we are in- 

 sensibly led to the philosophy of the case. If we observe the 

 gills and tail of the tadpole disappear, we must, as M. Quatre- 

 fages says, exclaim, ' ' Here are organs that become atrophied or 

 dwindle." If we compare the abdomen of a young crab with 

 that of the adult animal, we conceive the idea of " arrested 

 development," and if we observe the Lernea* having its limbs, 

 which first acted as oars, changed into a kind of anchor to 

 fasten it to its prey, we cannot but admire the way in which 

 nature appropriates an existing organ to a novel use, and we 

 find the idea of ' ' transformation." In these and similar transi- 

 tions there is nothing violent, but all goes on in measured 

 order and progression. In our author's words, "the gills of 

 the tadpole do not fall off to make room for luugs ; the tail is 

 not detached, because the legs are ready. No ; as the one 

 pushes on its growth, with bones, muscles, nerves, and vessels, the 

 other diminishes in all its parts. Molecule by molecule the one 

 is absorbed; molecule by molecule the other is built up." The 

 moults of crabs and other Crustacea do not prove exceptions to 

 this rule, for although the actual change of the hard integu- 



* Described by Mr. Brady, in our July number.] 



