CHAPTER II. 



MOLLUSCA. 



I SHALL treat of the Mollusca before the Articulate, 

 because as a group their intelligence is not so high. 

 Indeed, it is not to be expected that the class of 

 animals wherein the * vegetative ' functions of nutri- 

 tion and reproduction predominate so largely over the 

 animal functions of sensation, locomotion, &c., should 

 present any considerable degree of intelligence. Never- 

 theless, in the only division of the group which has 

 sense organs and powers of locomotion highly developed 

 viz., the Cephalopoda we meet with large cephalic 

 ganglia, and, it would appear, with no small develop- 

 ment of intelligence." Taking, however, the sub-king- 

 dom in ascending order, I shall first present all the 

 trustworthy evidence that I have been able to collect, 

 pointing to the highest level of intelligence that is at- 

 tained by the lower members. 



The following is quoted from Mr. Darwin's MS. : 



Even the headless oyster seems to profit from experience, 

 for Dicquemase (' Journal de Physique,' vol. xxviii. p. 244) 

 asserts that oysters taken from a depth never uncovered by the 

 sea, open their shells, lose the water within, and perish ; but 

 oysters taken from the same place and depth, if kept in reser- 

 voirs, where they are occasionally left uncovered for a short 

 time, and are otherwise incommoded, learn to keep their shells 

 shut, and then live for a much longer time when taken out of 

 the water. 1 



1 This fact is also stated by Bingley, Animal Biography, vol. iii. 

 p. 454, and is now turned to practical account in the so-called ' Oyster- 

 schools ' of France. The distance from the coast to Paris being too 

 great for the newly dredged oysters to travel without opening their 

 shells, they are first taught in the schools to bear a longer and longer 

 exposure to the air without gaping, and when their education in this 

 respect is completed they are sent on their journey to the metropolis, 

 where they arrive with closed shells, and in a healthy condition. 



