V. CEPHALOPODA. 



393 



It swells at its base to a sac in which the peripheral end is enclosed. 

 This part contains a canal for the spermatophores, cuts loose from 

 the male, and can creep about for days in the mantle chamber of 

 the female. Since it appears as if an independent animal, it was 

 first described as a parasitic worm under the name Hectocotylus. 

 Later it was regarded as a rudimentary male cephalopod. 



The eggs are either fastened singly to aquatic plants or are laid in large 

 gelatinous masses. They are rich in yolk, and in consequence undergo par- 



FIG. 395. Two stages of the germinal area of Sepia. (From Balfour, after Kolliker.) 

 cm, anus ; br, ctenidia ; /, siphon folds ; wi, mouth ; wit, mantle with shell gland ; 

 oe, eye ; p, head lobes ; 1-5 arms. 



FIG. 396. Embryos of LoUgo pealei (prig.), o, arms ; e, eyes ; /, fin ; g, ctenidia ; h, ot- 

 ocyst ; w, mantle ; s, siphonal folds and siphon ; v, anus ; y, yolk sac. 



tial discoidal segmentation (fig. 103). The blastoderm, on the end of the 

 oval egg, forms the anlagen of the separate organs (eyes, arms, siphon, and 



