Prof. Owen on Life and Species. 47 
being rendered by Natural Selection, more and more aquatic 
in their structure and habits, with larger and danger mouths, 
till a creature was produced as monstrous as a whale,’ 
The idea which Mr, Darwin persuades himself that he orig- 
inated in addition to Lamarck’s ‘influence des circonstances 
sur les actions et les habitudes des animaux et de celle des ac- 
tions et des habitudes de ces corps vivans, comme causes qui 
modifient leur organization et leurs parties’ is most intelligibly 
illustrated in the paper in which he first communicated his 
views to the Linnean Society. It is by ‘an imaginary exam- 
ple from changes in progress on an island ’:—‘ Let the organi- 
zation of a canine animal which preyed chiefly on rabbits, but 
sometimes on hares, become slightly plastic ; let these same 
changes cause the number of rabbits very slowly to decrease, 
and the number of hares to increase : the effect of this would 
be that the fox or dog would be driven to try to catch more hares; 
his organization, however, being slightly plastic, those individ- 
uals with the lightest forms, ongest limbs, and best eyesight, 
let the differences be ever so ; small, would be slightly favored, 
and would tend to live longer, and to survive during that time 
of the year when food was scarcest ; they would also rear more 
young, which would tend to inherit those slight _atloapecar 
e less fleet ones would be rigidly destroyed. I ¢ 
more reason to doubt that these causes in a cain: nera- 
tions would pome a marked effect, and adapt the form of 
modifications aménent des effets nuisibles, les animaux qui 
les éprouvent cessent d’exister, pour étre remplacés par d’au- 
tres, avec des formes un peu changées, et changées a la conve- 
nance des nouvelles circonstances.’{ 
The modifications on which Geoffroy Saint-Hilaire laid chief 
Stress were those assumed to have affected the ambient me- 
ium, the mode of operation of which in the origin of species 
he thus exemplifies :—‘ Mon Mémoire, traitant de Vinfluence 
des milieux ambians pour modifier les formes animales, montre 
searpaag la quantité décroissante de l’oxygéne, telacaeunaell 
aux autres composans de l’atmosphére, a pu forcer urfaces 
cutanées des embryons, premier et principal age des actes re- 
Spiratoires, 4 s’ouvrir davantage, 4 gagner, dans une raison in- 
verse du volume existant de Poxygéne,. an de prod alone 
au moyen de plus larges anfractuosités dans le — 
* This conclusion of the passage is omitted in later editions. 
ccexcrx’’, p. 79. 
i CI, p. 49. Bot sce he remarks on this in ca p-A04 and ca ES 
a i 
eet ie et 
