118 EVOLUTION AND DOGMA. 



Now, the interesting fact in connection with the 

 development of this curious animal is, that the vari- 

 ous stages through which it passes can be paralleled 

 by organisms which remain permanently in the con- 

 ditions in which the amphioxus rests but temporarily. 



The simple unicellular monad illustrates the in- 

 cipient condition or first stage of the amphioxus. 

 The second stage is paralleled by the pandorina, 

 which is but a group of cells, each similar to the 

 monad, living together in a common capsule. The 

 third stage is represented by the remarkable salin- 

 ella, which is a tubular structure composed of a 

 single layer of simple, monad-like cells. The fourth 

 condition is found in a common fresh-water volvox, 

 which, like the blastula stage, is an organism con- 

 sisting of a hollow sphere composed of a single 

 layer of simple flagellate cells. 



The four organisms just mentioned do not, it is 

 true, constitute a lineal series, a series, namely, in 

 which the more complex is genetically derived from 

 the simpler. But they prove, nevertheless, that all 

 the earlier temporary stages of the amphioxus, the 

 several curious embryonic conditions through which 

 it passes, can be paralleled by organisms which 

 have an actual permanent existence as adults, and 

 which are classed as so many distinct species. This, 

 to students of embryology, is a very remarkable 

 fact, and to the evolutionist, who believes that the 

 history of the individual is but a recapitulation of 

 the history of the race, it is profoundly suggestive and 

 significant and seems to indicate unmistakably the 

 derivative origin of higher from lower forms of life. 



