PEDIGREE OF VERTEBRATE ANIMALS. 



2SI 



evolutionary history of the individual. But though all 

 vertebrate animals testified their family connection by 

 agreeing inter se in the distribution of the germ as well 

 as in the fundamental important organs, the spinal cord 

 and the veretebral column, every token of their descent 

 from inferior animals, which is unconditionally demanded 

 by the theory, seemed to be entirely wanting. In other 

 words, it seemed that in all vertebrate animals the mem- 

 ory of their original derivation had been obliterated by 

 curtailed development (comp. p. 211). Thus the case 

 remained until Kowalewsky a few years ago studied the 

 development of the lancelet (Amphioxus), the lowest 

 vertebrate animal known, and showed that in this crea- 

 ture the typical phenomena of vertebrate development 



FIG. 22. — Larva of the Lancelet after Kowalewsky. 



are preceded by the phases required by the theory. We 

 have already made acquaintance with this form of de- 

 velopment (p. 51, &c.), and we here again point out its 

 profound significance. It is only when the Amphioxus 

 has passed through the phase of the vibrating, sac-like 



