188 GENERAL ZOOLOGY 



The Squid. In the waters of the Grand Banks of New- 

 foundland and southward to Massachusetts the members of 

 a species of squid, Ommas'trephes illecebro'sa (Fig. 96), occur 

 in great numbers. They capture small fishes, and are them- 

 selves prey for cod and other large fishes. 



The body of the squid is composed of a head and a slender, 

 conical portion, the former having a pair of large, movable 

 eyes (Fig. 96, G). Arising from the head-region are ten long, 

 club-shaped arms (Fig. 96, 1), corresponding morphologically 

 to the foot of the Pelecypoda and the Gasteropoda. Two of 

 the arms are longer than the other eight, but all are provided 

 on part of the inner surface with many sucking-disks, adapted 

 to holding the prey. The mouth has two horny jaws, resem- 

 bling in appearance the bill of a parrot turned upside down. 

 The tongue is adapted to rasping. 



The conical portion of the body is the mantle (Fig. 96, 2), 

 highly modified by the existence of strong, muscular bands. 

 Part of the space within the muscular mantle is occupied by 

 the internal organs inclosed in a body-cavity. The remainder 

 of the space, the mantle-cavity itself, connects with the out- 

 side by a narrow opening (Fig. 96, 5), at either side of the 

 neck, and also by the siphon (Fig. 96, 4). A pair of feather- 

 shaped gills, one attached to either side of the body, lies in 

 the mantle-cavity. Imbedded in the tissue of the mantle, 

 on the side opposite the surface shown in the figure, there 

 is a long, pen-shaped structure composed of chitinous mate- 

 rial. This is supposed to be the homologue of the shell of 

 Pelecypoda and Gasteropoda. The sexes are separate. 



In locomotion the squid contracts and relaxes the circular 

 muscles of the mantle, alternately decreasing and increasing 

 the volume of the mantle-cavity. During relaxation, water 

 enters the mantle-cavity at the sides by the neck, a valve 

 in the siphon being closed; in contraction the valves at 

 the side openings are closed and the water is discharged 



