98 Mr Carpenter on Unity of Function 



usually regarded as peculiar to the cephalopodes.* No inferior 

 group of mollusca presents such remarkable approximations to 

 the class of fishes in any stage of development ; and in none of 

 them do we observe that symmetrical form and elongation of 

 the trunk which is so prominent a feature in the structure of 

 the naked cephalopodes. 



We find among the classes which make up the sub-kingdom 

 radiata, a still greater tendency to pass into one another ; so 

 that it is almost impossible to fix witli precision the limits to 

 each ; and every botanist is aware, that however definitely even 

 the primary divisions of the vegetable kingdom may be formed, 

 many obstinate transgressors of their boundaries will be met 

 with, Avhich exhibit a very troublesome fondness for their 

 neighbours' domains. 



Dr Barry has quoted from Burmeister the very ingenious 

 remark, that the osteozoa (vertebrata) unite in themselves the 

 development of the nutritive system, which is characteristic of 

 the gastrozoa (mollusca) and the locomotive apparatus of the 

 arthrozoa (articulata). This is a beautiful confirmation of the 

 arrangement of the invertebrata, suggested by Lamarck, who 

 regarded tlie mollusca and articulata as forming two parallel 

 lines commencing with the radiata below, and terminating in 

 the vertebrata above ; each has its own characters of elevation 

 and degradation, and neither can be considered as in every re- 

 spect superior to the other. It appears to me, that, in the 

 nervous system of the vertebrata, we may trace the combined 

 characteristics of those of the mollusca and articulata. In the 

 former we find a circle of ganglia around the oesophagus, spe- 

 cially connected with the organs of sense, and therefore with 

 the function of nutrition ; and in their higher species, these 

 ganglia are almost entirely supra-oesophageal, and thus pass 

 into the cerebral ganglia of the vertebrata, whose spinal cord 

 on the other hand (which is now generally regarded as in itself 

 an originator of power, if not also a seat of sensation), being 

 specially connected with the locomotive organs, is a fair repre- 

 sentation of the double nervous column possessed by the typical 

 articulata. Whilst, therefore, this system, being necessarily 

 connected with all the other organs of the body, unites in the 



* Cyclopaedia of Anatomy, vol. i. p. 525. 



