18 BRITISH MARINE TESTACEOUS MOLLUSCA: 



Sixth Division. 



CEPHALOPODA DIBRANCHIATA. 

 Bisexual. 



These singular and highly organized animals are distributed 

 in two families : the Octopodidce include the genera Eledona 

 and Octopus; the Decapodidte, Loligo, Sepia, Sepiola and 

 Spirula : they all creep and swim. They are elaborately and 

 anatomically described and illustrated by M. Cuvier in his 

 memoirs, and by Professor Owen in the second part of the 

 second volume of the ' Zoological Transactions/ We have 

 merely mentioned these animals to preserve intact the chain 

 of the synopsis. To attempt to add novelty to this almost 

 exhausted subject would be a vain and fruitless labour. 



This is a most aberrant group, and cannot be placed in 

 line ; they are the most advanced in composition of the yet 

 discovered undoubted Mollusca; but there appears so large 

 an hiatus between them and the class they terminate, that 

 they can only be considered an anomalous lateral branch. 



I have now finished a limited analysis of my method of the 

 distribution of the British marine testaceous Mollusca. I am 

 led to think the sexual arrangement natural and well-founded, 

 as it cannot fail to have been observed that as the generative 

 influences are more or less perfect, there is a corresponding 

 energy and activity. If we cast a glance at the strict herm- 

 aphrodites, as the Acephala and Patella tribes, we find them 

 either fixed or of the most limited locomotion ; but as soon as 

 the generative structure is improved, the animals become 

 more lively and locomotive. This view is exemplified in the 

 hermaphrodites with congression, for instance, in the natatory 

 Gasteropoda and Pulmonifera ; but when bisexuality is esta- 

 blished, there is an evident increase of motion, functions, and, 

 I may say, even of intelligence and structural composition. 

 And lastly, on arriving at the most highly developed genera- 

 tive influences that can attach to the Invertebrata, we see an 

 energy and activity that even exceed those qualities in some 



