PEEFACE. Vll 



and kind of evidence — Observation, Dissection, or Es- 

 periment — on which they rest ; so that the source of 

 error, wherever there is error, may be detected. 



The most startling of the new views, that, namely, 

 on the identity of Growth and Generation, has re- 

 cently received striking confirmation in the admirable 

 researches of Professor Huxley on the Aphides — re- 

 searches which render the facts I have observed in the 

 development of Polypes less paradoxical than they 

 originally appeared. 



JoMuary 1858. 



