68 THE THEORY OF EVOLUTION 



trace of limbs is to be found on dissection, but in 

 certain snakes the rudiments of limbs are to be 

 detected. Leaving aside all preconceptions, which 

 is the more probable explanation of such phenomena, 

 the theory of special creation or the theory of evolu- 

 tion? 



Even if it were admitted that all rudimentary 

 organs and structures found in the adult have a 

 certain unknown use and value, no one could main- 

 tain this with regard to the countless instances of 

 structures which are developed in the embryo, but 

 disappear entirely before birth. It is possible to 

 mention but a very few of such instances out of the 

 great number that have already been observed and re- 

 corded, but these few will suffice to illustrate the 

 principle involved. 



>( Examples of this may be cited from the most 

 widely different groups: in the embryo of insects, 

 especially of beetles, pairs of legs are formed within 

 the egg, not only on the head and thorax, but also 

 on the abdomen, but while those on the head are 

 transformed into mouth-parts, those on the thorax 

 are farther developed in their jointing and muscula- 

 ture to be locomotive legs, those on the abdomen 

 are again resorbed. In many fresh- water worms, the 

 eggs of which are laid in a cocoon, from which they 

 are hatched as a finished, minute, crawling worm, 

 larval organs are nevertheless formed, which recall 

 those of the Trochophore, the larva of the original 

 worms, which swims freely in the sea. However, 



