134 BIOLOGICAL LECTURES, 



Whether phylogerontic characteristics are inherited or simply 

 have a common origin, the facts of correspondence remain the 

 same, and this enables us to speak confidently of the whole 

 cycle of the ontogeny or ontocycle as more or less exactly par- 

 allel with the cycle of the phylogeny or phylocycle. 



Even in such general statements it is perhaps necessary to 

 caution readers that the retrogressive phases above mentioned 

 are entirely those that apparently occur first in the gerontic 

 stages of the ontogeny of more or less progressive forms of the 

 same genetic stock. There are in some groups, especially 

 among parasites, also introduced, adaptive stages of a retro- 

 gressive nature that are not in any sense gerontic, and these 

 are not included in these statements. 



Connected organisms, according to such views, are looked upon 

 as complex associations of series diverging like the branches of 

 a tree, each branch or phylum passing through a stage of 

 phyletic rejuvenation represented by the more or less primitive 

 forms with which it begins. These radicals are more or less 

 closely related or divergent as compared with the common 

 radical stock or trunk, according to their position in time or 

 their grade in natural classification, but become in turn starting 

 members of new series. These series, if they take a normal 

 course, first progress in structure and then retrogress, but ever 

 proceed onwards in time and space until extinction closes their 

 career. 



All naturalists, even at the present time, have not acquired 

 the habit of looking upon organisms as in continuous motion 

 and unceasingly changing while moving onwards through time 

 and space. Farlow treats the errors due to this omission in 

 his paper, read before the Boston meeting of the American 

 Association for the Advancement of Science in 1898, on "The 

 Conception of Species as affected by Recent Investigations on 

 Fungi." This high authority writes as follows: " Our so- 

 called species are merely snapshots at the procession of nature 

 as it passes along before us. In any case it represents only a 

 temporary phase, and in a short time will no longer be a faith- 

 ful picture of what really lies before us, for we must not forget 

 that the procession is moving constantly onwards, and at a 



