SQUID: LABORATORY WORK. 



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 ? 

 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. 



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 sim ilarly arranged 

 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 

 middle, beginning at the free edge and carrying the incision 

 to the end of the body. This lays open the mantle chamber. 



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