The Presidential Address. 
85 
tlie species is protected from Nature’s strife, it may persist 
unaltered or with only slight modification throughout whole 
geological periods, as we see in the numerous low forms of 
aquatic life, and higher in the scale in such types as Lepido- 
siren and Ornitliorliynchus , which Darwin speaks of as “living 
fossils.” 26 Or again, through parasitism or other causes, a 
species may he driven to a mode of life in which high 
organisation is not only useless, hut may he actually detri¬ 
mental to its possessor. In such cases natural selection, 
having only the good of the species in view, would bring 
about a more lowly-organised condition in the adult animal, 
while the younger stages, by the law of homoclironic heredity, 
would retain the higher structure of the ancestral form. 
This principle of “ degeneration ” is seen in such groups as 
the Ascidians, the parent-stock of all the vertebrate animals; 
in the barnacles, which are degenerate Crustacea; and in the 
Mexican Axolotl. The development of Darwinism in this 
direction will be found in works by Anton Dokrn 27 and Prof. 
E. Pay Lankester. 28 
Before concluding this necessarily imperfect sketch of 
Darwin’s chief work, there remain a few considerations to 
which I should like to direct attention. I may remind you, 
with reference to the various objections that have from time 
to time been urged against the theory of selection, that there 
has not been a more candid critic of this theory than Mr. 
Darwin himself, and in point of fact it is not going too far to 
say that hardly any difficulty of importance has been raised 
which was not suggested in the 4 Origin of Species.’ I will, 
with your permission, dwell briefly upon one or two objections 
which are still occasionally to be heard. 
Variability, the basic factor of species-transformation, is 
26 Just as this Address was completed there appeared in ‘ Nature ’ an 
interesting article by Prof. Hubrecht, in which the subject of persistent 
forms of life is treated in a somewhat novel way, under the title of “ The 
Hypothesis of Accelerated Development by Primogeniture, and its place 
in the Theory of Evolution.” Yol. xxvii., pp. 279 and 301. 
27 ‘Der Ur sprung der YTirbelthiere und das Princ-ip des Functionswech- 
sels,’ Leipzig, 1875. 
28 ‘ Degeneration, a Chapter in Darwinism,' Macmillan, 1880. 
