xxvn DEVELOPMENT 331 



body of the female. In the common Dog-fish (Scyllium) 

 they are laid shortly after impregnation, each enclosed in a 

 horny egg-shell : in the Piked Dog-fish (Acanthias) and the 

 Smooth Hound (Mustelus) they are retained in the oviduct 

 until the adult form is assumed. 



