226 Studies in the Theory of Descent. 



phyletic stage ; and in its third stage ; the fourth 

 phyletic stage is represented, so that little imagina- 

 tion is required to anticipate that in the second 

 stage the third or second phyletic stage would be 

 pictured. 



If we tabulate the development of the various 

 species, indicating the ontogenetic stages by 

 Arabic numerals, and the stages of the phylogeny 

 which are reached in each stage of the ontogeny 

 by Roman numerals, we obtain a useful synopsis 

 of the series of developments, and, at the same 

 time, it shows how many gaps still remain to be 

 filled up in order to complete our knowledge even 

 of this small group of species. 



TABLE OF DEVELOPMENT OF THE SPECIES OF DEILEPHILA. 



