GENERAL ANATOMY OF THE SQUID. 361 



4. Outside the brain and inside the integument of the 

 head notice the cut surfaces of the upturned edges of the 

 head cartilage (e, k). 



FIG. 189. 



FIG. 189. Transverse section through the head of a young specimen 

 of Loligo Pealii; magnified about twenty diameters. (Drawn from nature 

 by W. K. Brooks. ) 



. Circular muscles of siphon, b. Cavity of siphon, c. Longitudinal 

 muscles of siphon. tZ. Venae cavae. /. Pedal ganglion, g. Optic com- 

 missure, h. Optic ganglion, i. Peripheral layer of white matter. 

 j. Peripheral layer of gray matter. I. (Esophagus, m. Cerebral ganglion. 

 e, k. Cephalic cartilage. 



5. On the ventral surface of the head notice the section 

 of the upper end of the siphon (b), the wall of which con- 

 sists of longitudinal muscles (c, c, c) and circular muscular 

 fibres (a). 



