420 



MANUAL OF ZOOLOGY. 



Pearly Nautilus the arms are numerous and are devoid of 

 suckers. 



In all the Cuttle-fishes, the mouth is placed in the centre of 

 the " foot," and it is by a splitting up of the margins of the 

 foot into long muscular processes, that the " arms " are pro- 

 duced. The arms are always symmetrically arranged in a 

 dorsal, a ventral, and two lateral pairs ; and the " tentacles " 

 (when present) are placed on the ventral surface, between the 

 3d and 4th pairs of arms. The tentacles may or may not be 

 retractile into pouches placed below the eyes, and their length 

 may be many times greater than that of the body. They are 

 organs of prehension ; and the arms are in addition employed 



by the animal in locomotion, 

 enabling it to creep along the 

 sea-bottom head downward. 

 In all the Decapod, and 

 in some of the Octopod 

 forms, the sides of the body 

 are produced into muscular 

 expansions or fins (figs. 224 

 and 231), with which the 

 animal swims head foremost. 

 In all the Cephalopods, also, 

 the lateral margins of the 

 foot ("epipodia") are either 

 placed in apposition (Naut- 

 ilus] or are actually united 

 (Cuttle - fishes), in such a 

 manner as to form a muscu- 

 lar tube, known as the "fun- 

 nel." The funnel is placed 

 on the lower surface of the 

 body, with its anterior ex- 

 tremity projecting beyond 

 the mantle, while it opens 

 behind into the pallial cham- 

 ber. It serves for the elim- 

 ination of the water which 

 has been used in respiration, 

 and the out -going currents 

 also carry away with them the excretions of the kidneys and 

 of the ink -sac, together with the faeces. By the contractions of 

 the mantle, the water contained in the pallial sac can also be 

 driven through the funnel in a succession of jets, driving the 

 animal backwards through the water. 



Fig. 225. Diagram o a Cuttle-fish^(altered 

 fr< 



iglis 

 g Gill ; / Funnel ; o Ovary ; 



rom Huxley). 

 ganglia ; / Li 



tn Mandibles ; n Cerebral 

 ver ; p Intestine ; i Ink-bag ; 

 Cuttle-bone. 



