SQUID. 



EXTERNAL FORM. 



The head, separated from the body by a 'neck/ bears at 

 its anterior end a circle of tentacles: how many? Are 



/ 



all of these of equal length? If not, which pair is the 

 longer, numbering them from the dorsal surface? On 

 the side of the head are the eyes; behind the eye is a fold 

 of the skin, the olfactory organ. The body is surrounded 

 with a mantle, bearing at the posterior end a pair of large 

 fins. Is the mantle joined to the body all around? If not, 

 where is it attached? Projecting from the mantle opening 

 is the end of a fleshy tube, the siphon. The side of the 

 body on which the siphon occurs is usually called the ven- 

 tral side. Can the siphon be compared in structure to 

 that of the clam? 



Sketch the squid from the side, showing these points, not 

 omitting the color spots (chromatophores) . 



Examine the tentacles more carefully. On their inner 

 surfaces see the stalked suckers. Are they similarly ar- 

 ranged on all the arms? Examine a sucker with the hand- 

 lens, making out the fleshy lip, the horny hooks, and a 

 fleshy bottom (piston) in the central cavity. Sketch a 

 sucker, considerably enlarged. 



INTERNAL STRUCTURE. 



Place the squid in the dissecting-pan, siphon uppermost. 

 Cut the mantle longitudinally a little to one side of the 



103 



