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no place for Amphioxus among Annelids, nor among the primor- 

 dial vertebrates, as it lacks almost all that they possess. Yet 

 nothing can be gained by excluding Amphioxus from the verte- 

 brates, for it is so connected with the Cyclostome fishes that it 

 cannot be placed at any great distance from them, while on the 

 other hand it is so related to Ascidians that the latter must be 

 included among the vertebrata. Dohrn then proceeds with a 

 long argument to show that the Cyclostome fishes are degenerate 

 from a higher type of fishes, and that Amphioxus is a result of 

 still further degeneration. He shows how their mode of life 

 necessitates many of the modifications they have undergone, and 

 that the diversities of the details of structure in Cyclostomes are 

 inconsistent with their being viewed as representing stages in 

 upward development. Finally, the larva of Ascidians is repre- 

 sented as a degenerate fish, a degenerate Cyclostome possibly, 

 which carries to the extreme all the departures of the latter from 

 the fish type. The most important element in this degeneration 

 results from the fact that Ascidians, instead of being attached to 

 fishes or to any objects from which they can derive nutriment 

 are fixed to stones, plants, or to such parts of animals (cephalo- 

 thorax of Crabs, tubes of tubicolous annelids) as do not afford 

 them nourishment. Consequently, they have lost the old mouth 

 in the organ of attachment, homologous with that of all verte- 

 brates and have developed a new one, homologous with the nasal . 

 passage of Myxine. Thus we can explain the astonishing fact, 

 that the mouth opening of the Ascidian larva has a communica- 

 tion with the fore wall of the so-called cerebral visicle. The 

 most patent objection to Dohrn's view about Amphioxus is that 

 it fails to account for the development of a many - segmented 

 respiratory apparatus as a degeneration for a higher animal with 

 a small number of gill arches. It would appear far more rea- 

 sonable to suppose Amphioxus to be a degeneration from a much 

 lower elevation than the Cyclostome type, namely, from some 

 stage where the respiratory apparatus retained the multiserial 

 character derived from its Annelid forefathers. The keynote of 

 this reasoning is to be found in the principle of transformation 

 of functions. It is stated thus: "The transformation of an organ 



