Lll 



MASS. 



LOLIGO PEALII Lesueur 



Material. Loligo pealii is found along the Atlantic Coast 

 in depths below low-water mark and down to about fifty 

 fathoms. It should be preserved in formalin. Injection of the 

 circulatory system is not necessary. Each student should re- 

 ceive if possible one specimen of each sex. 



Descriptive Part 



Loligo pealii or the common squid is a typical representative 

 of the class Cephalopoda or those molluscs in which part of the 

 modified foot is situated at the end of the head and forms the 

 tentacles and arms surrounding the mouth. At first sight it 

 looks as if the squid were structured on a different plan from 

 other molluscs, but the difference is more of a physiological than 

 of a morphological kind. In order to understand the structure 

 of the squid one should place it head down, hind end up. In 

 this position the ventral surface is formed by the arms, tentacles 

 and funnel, the latter being also part of the modified foot. The 

 mouth is at the anterior end, the funnel at the posterior end of 

 the animal. The dorsal surface is drawn out in the shape of a 

 long cone in which we may recognize an antero-dorsal and a 

 postero-dorsal region or surface. In other words, the squid is 

 an excessively humpbacked animal in which this condition has 

 deeply modified the functions of the various regions of the body. 

 The squid swims forward or backward more or less in the line of 

 its long axis and with the postero-dorsal surface down. This po- 

 sition presents the least resistance to locomotion in the water. 

 The postero-dorsal surface functions therefore as the ventral 

 surface, the antero-dorsal as the dorsal surface and the dorso- 



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