176 INSTINCT OF MOLLUSCA. 



which floats around them, in its varied temperature, in the 

 work of capturing their prey, in the imbibition and expul- 

 sion of the fluid necessary to respiration, &c., they will find 

 both business and amusement ; and, in due season, love 

 visits even these phlegmatic things, when " icy bosoms feel 

 the secret fire." 



Yet, doubtless, from their general inertness and hebe- 

 tude, we are led to infer that the sensations and passions of 

 the molluscans are of a cold, and low character, — an inference 

 confirmed, perhaps, by the character of the nervous system, 

 somewhat analogous to the sympathetic system of nerves in 

 the higher classes. The inference, however, may be erro- 

 neous : it is more certain that their organization is un- 

 fitted for the genesis of those surprising instincts which, 

 in insects, render the limits between them and the opera- 

 tions of reason or intelligence very obscure and dubious. 

 The instincts of the mollusca seem, in fact, to be almost 

 limited to some simple devices for self-preservation. When 

 in danger, the Ascidiae ejaculate with force the water 

 contained in the great branchial cavity, and drive away their 

 weak foes ; and many of the burrowing Bivalves use the 

 same defence, sinking at the same time deeper in their 

 furrows. The naked Gasteropods shrink within themselves, 

 and curtail every tentaculum and process when sudden 

 danger comes upon them ; while the shelled tribes retreat 

 hastily within their strongholds,* excepting one or two 

 which, like the Helico-limax lamarckii and the Nanina?, 

 endeavour to escape by additional speed. There is indeed 

 many degrees among them in their watchfulness and cau- 

 tion, for some, when touched during their walk, are only 

 momentarily arrested, and scarcely heed the annoyance ; 

 while tlie majority, perhaps, are so sensitive that they 

 retire within their security from a slight cause ; and remain 

 a long time in their concealment. -j- To these ordinary re- 



* " Fool. — Can'st tell how an oyster makes his shell? Lear: — No. Fool. 

 — Nor I neither ; but I can tell why a snail has a house. Lear. — Why 1 

 Fool. — Why to put his head in ; not to give it away to his daughters and 

 leave his horns without a case." — K. Lear, act i. sc. v. 



t Perhaps the most singular instance of instinctive action in a mollusk, 

 is that mentioned by Lister of tlie Helix pomatia. " De Cochlea ter- 

 rcstri, Pomatia Gesneri dicta, illud singulare, ineunte Junio, vidi ; scilicet 

 in dumetis juxta Ashstead, in vicinia Epsam, ubi passim occurrunt ; earum 

 non paucas, prunorum sylvestrium arbusculas scandissc, singulasque coclileas 

 longissima spina insedisse, qualibus istse arbusculte donantur, ad digitum ct 

 amplius, tanquam per medium corpus transfixa ; at cum rem accuratius ex- 

 aminassem, spinam medio pede positam inveni, et sic una cum eo introduc- 

 tam, Atque hujus quidem rei una ea utilitas esse potuit, ad sedem sibi 



