Contents. xxxv 



ON THE FINAL CAUSES OF TRANSFORMATION 



(continued). 



III. 



THE TRANSFORMATION OF THE MEXICAN AXOLOTL 

 INTO AMBLYSTOMA. 



Introduction, p. 555. 



Experiments, 558. Significance of the facts, 563. The Axolotl 

 rarely or never undergoes metamorphosis in its native country, 565. 

 North American Amblystomas, 570. Does the exceptional transfor- 

 mation depend upon a phyletic advancement of the species? 571. 

 Theoretical bearing of the case, 574. Differences between Axolotl 

 and Amblystoma, 575. These are not correlative results of the sup- 

 pression of the gills, 578. Explanation by reversion, 581. Cases of 

 degeneration to a lower phyletic stage : Filippi's sexually mature 

 " Triton larvae," 583. Analogous observations on Triton by Jullien 

 and Schreibers, 591. The sterility of the artificially produced Am- 

 blystomas tells against the former importance of the transformation, 

 594. It is not opposed to the hypothesis of reversion, 596. 

 Attempted explanation of the sterility from this point of view, 597. 

 Causes which may have induced reversion in the hypothetical Mexican 

 Amblystomas, 600. Saltness of the water combined with the drying 

 up of the shores by winds, 604. Consequences of the reversion 

 hypothesis, 609; Systematic, 609; an addendum to the "funda- 

 mental biogenetic law," 611 ; General importance of reversion, 612. 

 Postscript ; dryness of the air the probable cause of the assumed re- 

 version of the Amblystoma to the Axolotl, 613. Addendum, 622. 



IV. 



ON THE MECHANICAL CONCEPTION OF NATURE. 



Introduction, p. 634. 



Results of the three foregoing essays : denial of a phyletic vital 

 force, 634. Application of these results to inductive conclusions with 

 reference to the organic world in general, 636. The assumption of 

 such a force is opposed to the fundamental laws of natural science, 

 637. The "vital force" of the older natural philosopher, 640. 

 Why was the latter abandoned? Commencement of a mechanical 

 theory of life, 642. 



