Crustacea. 



6623 



this fusion, which here embraces but four ganglia, in the higher types 

 embrace as well the seven succeeding. This is more or less perfect 

 in its completion in different animals. In the Macroura, that is the 

 lobster, the long-tailed order, the union of these several ganglia 

 (according to Edwards) form one long ganglion, like several in con- 

 junction ; but in the Brachyura, or short-tailed species, they are more 

 perfectly formed into one large ganglion ; and the only difference 

 observable between the nervous systems in the swimming and the 

 spider crabs consists in there being a hollow space in the centre of 

 the large ganglion, or mass, in the former, whilst it is filled up and 

 solid in the latter. It has on this account always been orthodox, from 

 Edwards and Audouin, who first carefully described the nervous sys- 

 tem of Crustacea, down to Dana, the latest who has written systema- 

 tically upon the subject, to consider that of the spider crabs as being 

 the most perfectly fused, and therefore highest in grade. 



But it should be remembered that that which gives rank to all 

 animals is the greater or less degree of its intelligence and instinctive 

 force. All consciousness of power and existence in animals comes 

 through the senses, and the organs endowed with the capability of 

 sensation are supplied by nerves that come directly from the brain. 

 We have, then, d priori, a right to assume that those organs which 

 are similarly endowed in the lower forms are supplied by nerves that 

 proceed from an organ which represents the seat of consciousness ; 

 and although it bears no resemblance to a brain, and in fact is 

 scarcely more if as important as the other ganglia of the body, yet 

 must be analogous to a brain. The antennae and the eyes receive 

 their supply of nerves from the first or supracesophagal ganglion, 

 which is the result of an union between the three most anterior 

 ganglia, and which are only separated in the Squilla, where the 

 anterior segments are not fused with the carapax. 



The antennae and the eyes are known, from external evidences, to 

 be organs of sensation, and therefore the mass from which their 

 nerves originate must be endowed with the capacity of receiving 

 impressions derived through those organs ; therefore it must be the seat 

 of consciousness. The more perfectly endowed the animal may be 

 with conscious power, the higher we should esteem its rank among 

 animals ; and in dissecting for the purpose of verifying this hypothe- 

 sis, w T e should anticipate a greater or more perfect development in 

 the appearance of those ganglia that supply the organs of sense, with 

 or without a corresponding degree in that of the other parts of the 

 nervous system. 



