IV.] MINUTE MODIFICATIONS. 



vertebrate fin-limb. In the ichthyosaurus, in the plesio- 

 saurus, in the whales, in the porpoises, in the seals, and in 

 others, we have shortening of the bones, but no reduction 

 in the number either of the fingers or of their joints, which 

 are, on the contrary, multiplied in Cetacea and the ichthyo- 

 saurus. And even in the turtles we have eight carpal 

 bones and five digits, while no finger has less than two 

 phalanges. It is difficult, then, to believe that the Avian 

 limb was developed in any other way than by a compara- 

 tively sudden modification of a marked and important kind. 

 How, once more, can we conceive the peculiar actions 

 of the tendrils of some climbing plants to have been pro- 

 duced by minute modifications ? These, according to Mr. 

 Darwin, 28 oscillate till they touch an object, and then em- 

 brace it. It is stated by that observer, that " a thread 

 weighing no more than the thirty-second of a grain, if 

 placed on the tendril of the Passiflora graeilis, will cause 

 it to bend ; and merely to touch the tendril with a twig 

 causes it to bend ; but if the twig is at once removed, the 



SKELETON OP AN ICHTHYOSAtTRTTS. 



tendril soon straightens itself. But the contact of other 

 tendrils of the plant, or of the falling of drops of rain, do 

 not produce these effects. 27 But some of the zoological and 

 anatomical discoveries of late years tend rather to diminish 

 than to augment the evidence in favor of minute and grad- 



06 Quarterly Journal of Science, 1866, pp. 257, 268. 

 97 "Habit and Intelligence," vol. i., p. 178. 

 6 



