XXviii INTRODUCTION. 



known that the lobster will live for a long time out of 

 water, provided the branchiae are occasionally bathed, so 

 as to keep them in a humid condition, whilst it will 

 die very soon on being confined in a small quantity of 

 water, without access to air. 



There has been considerable discrepancy in the state- 

 ments of different anatomists respecting the circulation in 

 the Crustacea. Messrs. Audouin and Milne Edwards* 

 have considered that " no other than the two great bran- 

 chial veins terminate in the lieart, and, consequently, only 

 pure aerated or arterial blood is propelled by it over the 

 general system ; the circulation is, in fact, the same as in 

 the Gasteropodous Mollusca; the ventricle is exclusively 

 systemic, and is provided with only two venous aper- 

 tures." Such is a summary of their opinion. The fact, 

 however, that the circulation is of a mixed kind was evi- 

 dently known to Hunter, and has been elaborately demon- 

 strated by Professor Owen in his more recent researches. f 

 A reference to the engravings from the Hunterian draw- 

 ings in the collection of the Royal College of Surgeons,^ 

 to that of the heart of the lobster by Professor Owen in 

 his lectures above referred to, and to the respective de- 

 scriptions of these figures, will show " that the heart, 

 instead of being purely systemic, is partly branchial, and 

 impels the blood, not through the body only, but also to 

 the respiratory organs." 



* RechercliGS Anatomiques et Pliysiologiques sur la Circulation dans Ics 

 Crustaces. Ann. des Sc. Nat. t. ii. 



t Lectures on the Comparative Anatomy and Physiology of the Invertebr. 



X Catalogue of the Physiological Series of Comparative Anatomy contained 

 in the Museum of the Royal College of Surgeons, vol. ii. Copied in Professor 

 Rymer Jones's " Animal Kingdom/' pp. 333-336, 



