V. CEPHALOPODA 



345 



yolk, which, enclosed in a cellular envelope, remains attached to the rest, near 

 the mouth, until it is absorbed in the growth of the young and the animal is 

 ready for hatching (lig. 361). 



Fro. 360. — Male of Argonaula argo (after Muller, from Hatschek). 1-4, arms 

 of right side; 1.-4., arms of left side; 3, heclocotylised arm, at the left in its sac, at tlie 

 right protruded. 



Fig. 361. — Embryos of Loligo pealei (orig.). a, arms; e, eyes;/, fin; g, ctenidia; 

 h, statocyst; m, mantle; s, siphonal folds and siphon; v, anus; y, yoLk sac. 



The Cephalopoda are e.xclusively marine. Some inhabit rocky shores, 

 others the high seas. All are carnivorous and in turn are preyed upon by fishes, 

 etc. Classification is based upon the number of gills and number and character 

 of the arms. 



