84 Laboratory Guide in Zoology- 



cylindrical body, covered by a mantle and tapering to 

 a point. See the distinct, slightly movable head. Find 

 the large eyes, the arms or tentacles, and the mouth be- 

 tween the bases of the arms. Find a fold in the mem- 

 brane directly back of each of the eyes : these are the 

 olfactory lobes. See the opening in the siphon tube 

 back of the head on the lower side of the body, and 

 the wide terminal fins toward the posterior end of 

 the body. 



II. — Study the tentacles. How many are there? How 

 do they vary in size.' Notice the two rows of suckers 

 on the inner margin of the tentacles : how are they 

 arranged .'' Of what especial use are the suckers .' 

 The pair of long arms are called the grasping arms : 

 what is their shape ? What is the arrangement of the 

 suckers upon them ? 



III. — Study the mouth. What is its shape.' Notice the 

 peristome. Open the mouth and notice the large chitin- 

 ous jaws. Which is the larger.' The mouth is sur- 

 rounded by projections of the skin : how many and of 

 what use are they .' 



IV. — Study the large eyes. Is their position an advan- 

 tageous one ? 



V. — Study the siphon tube, beneath the head and pro- 



jecting from between the mantle and the neck. Study 

 the structure of the orifice. 

 VI. — The body is enclosed in a mantle. From what do 

 the large terminal fins on the posterior third of the 

 body arise .' These fins are used for swimming. 

 Around the neck you will find a cavity. This is the 

 external part of the mantle cavity. A small projection 

 of the mantle over the middle of the head is the pen. 

 The squid can take water into the mantle cavity 



