346 



MANUAL OF ZOOLOGY. 



vertically like the beak of a bird ; together with an " odonto- 

 phore " or " tongue/' the anterior part of which is sentient, 



whilst the remainder is 

 covered with recurved 

 spines. The buccal cavity 

 (fig. 144), conducts by 

 an oesophagus into which 

 salivary glands usually pour 

 their secretion to a sto- 

 mach, from which an in- 

 testine is continued, with a 

 neural flexure, to open on 

 the ventral surface of the 

 animal at the base of the 

 funnel. In many cases 

 there is also a special gland, 

 called the "ink-bag," for 

 the secretion of an inky 

 fluid, which the animal dis- 

 charges into the water, so 

 as to enable it to escape 

 when menaced or pur- 

 sued. The duct of the 

 ink-bag opens at the base 

 of the funnel ; but this 

 apparatus is entirely want- 

 ing in the Tetrabranchiate 

 Cephalopods, where in con- 

 sequence of^the presence 

 of an external shell, this 

 means of defence is not needed. 



The respiratory organs (fig. 144), are in the form of two or 

 four plume-like gills, placed on the sides of the body in a 

 branchial cavity which opens anteriorly on the under surface of 

 the body. At the base of each gill, in the Cuttle-fishes, is a 

 special contractile cavity, whereby the venous blood returned 

 from the body is driven through the branchiae. In addition to 

 these accessory organs the so-called "branchial hearts " there 

 is a true systemic heart, by which the aerated blood received 

 from the gills is propelled through the body. In the higher 

 Cephalopods a capillary system of vessels intervenes, in most 

 cases at any rate, between the arteries and the veirs. The 

 admission of water to the branchiae is effected by the expansion 

 of the mantle so as to allow the entrance of the outer vater into 

 the pallial chamber. The mantle then contracts, and the water 



Fig. 144. Diagram of a Cuttle-fish 

 from Huxley), tit 



(altered 



Mandibles ; 11 Cerebral 



ganglia; /Liver; /Intestine: i Ink-bag; 

 g Gill ; ./Funnel ; o Ovary ; j Cuttle-bone. 



