Coming now to the cephalopoda, there is no doubt that if a larger sphere of opportunity permitted, adequate observation of these animals would prove them to be much the most intelligent members of the sub-kingdom. Unfortunately, however, this sphere of opportunity has hitherto been very limited. The following meagre account is all that I have been able to gather concerning the psychology of these interesting animals. According to Schneider,[17] the Cephalopoda show unmistakable evidence of consciousness and intelligence. This observer had an opportunity of watching them for a long time in the zoological station at Naples; and he says that they appeared to recognise their keeper after they had for some time received their food from him. Hollmann narrates that an octopus, which had had a struggle with a lobster, followed the latter into an adjacent tank, to which it had been removed for safety, and there destroyed it. In order to do this the octopus had to climb up a vertical partition above the surface of the water and descend the other side.[18] According to Schneider, the Cephalopoda have an abstract idea of water, seeking to return to it when removed, even though they do not see it. But this probably arises from the sense of discomfort due to exposure of their skin to the air; and if we can call it an 'idea,' it is doubtless shared by all other aquatic Mollusca when exposed to air. FOOTNOTES: [9] 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. [10] Bingley, _loc. cit._, vol. iii. p. 449. [11] _De l'Espèce et de la Classe_, &c., 1869, p. 106. [12] _A Londoner's Walk to Edinburgh_, p. 155 (1856). [13] _Descent of Man_, pp. 262-3. [14] The facts, however, in order to sustain such conclusions, of course require corroboration, and it is therefore to be regretted that Mr. Lonsdale did not experimentally repeat the conditions. [15] _Journal Linn. Soc._ vol. xiv. p. 406 _et seq._ [16] _Mag. Nat. Hist._ 1831, vol. iv. p. 346. [17] _Thieresche Wille_, § 78. [18] _Leben der Cephalopoden_, s. 21. CHAPTER III. ANTS.