752 ZOOLOGY SECT, xn 



ing Mollusca by its wonderfully high organisation, especially in 

 the nervous system and the eye, and there is nothing to indicate 

 close relationship with any of the lower classes, beyond the general 

 conformity to the molluscan plan of organisation, and the presence 

 of an odontophore. The Cephalopods form, in fact, a singularly 

 isolated group. Palaeontology has not hitherto given any indica- 

 tion of their origin, and embryology is equally silent, the absence 

 of a free larva, and the profound modification in development 

 produced by the enormous mass of food-yolk sharply separating 

 them from all other members of the phylum. 



