A SQUID 103 



Class : Cephalopoda 

 A SQUID {LOLIGO PEALI) 



The squid is a very common marine animal. It is gregarious 

 in its habits and swims about in large schools in search of its food, 

 which consists of crustaceans, , small fishes, etc. When alarmed 

 by the presence of its natural enemies, which are many kinds of 

 fishes, it clouds and darkens the water by ejecting into it an ink- 

 like fluid. The fresh animals are studied with greater profit than 

 those which have been preserved in alcohol, as this changes the 

 nature and appearance of many of the organs. The best pre- 

 servative is formalin. 



External Anatomy. Observe the cylindrical, bilaterally sym- 

 metrical body ; at one end is a pair of broad fins, and at the other 

 the movable head bearing ten arms, two of which are much 

 longer than the others. The mouth is at the base of and sur- 

 rounded by the arms, and the brown, horny beak may usually 

 be seen protruding partly from it. The large eyes are on the sides 

 of the head at the base of the arms. Each is covered by a cornea, 

 which is pierced by a small hole between the eye and the base of 

 the arms, so that sea water is admitted freely into the space be- 

 tween the cornea and the pupil, and may take the place of the 

 aqueous humor of the vertebrate eye. A transverse fold on the 

 side of the head between the eye and the body is the olfactory 

 organ. Observe the pigment spots, or chromatophores, which are 

 distributed over the body ; they are constantly changing in shape 

 and size during life, causing corresponding changes in the color 

 and appearance of the animal. 



The head and neck project from the large mantle cavity, into 

 which they can be partially withdrawn by means of powerful re- 

 tractor muscles, in very much the same way that a snail's head 

 and foot can be withdrawn into its shell. The siphon, or funnel, a 

 large, funnel-shaped organ at the base of the head, also projects 

 from it and can be similarly withdrawn. Gently probe the mantle 

 cavity and determine its extent. The mantle constitutes the 

 outer surface of the body. It will be seen to be a cylindrical 



