a 7 



ON THE CLASSIFICATION OF THE ANIMAL KINGDOM 

 BY THE DISTRIBUTION OF THE NERVES. 



BY F. M. BURTON, ESQ. 

 f Continued from page 54. ) 



No. II. 



We have now arrived at the completion of the first great division of 

 the animal kingdom — the Acrita; and have witnessed with interest the 

 gradual development of various organic structures in these lower orders of 

 life, from the sponges to animals possessing a regular digestive apparatus 

 and highly-developed organs of generation; but as yet no mention lias been 

 made of the nerves. It must not be supposed, however, that the animals 

 we have been considering do not possess a nervous system, but that, with 

 the aid of the most powerful microscopes, they have not as yet been 

 discovered. Professor Jones indeed hints at such a system existing in 

 several of the more highly organized types, but always alludes to the 

 subject with considerable doubt and hesitation. 



We now come to the second great division of the Animal Kingdom — 

 the Nematoneura, or animals with thread-like nerves, including the Coelel- 

 mintha, Bryozoa, llotifera, Epizoa, and Echinodermata; and, in the words 

 of the author, having hitherto seen "the digestive process carried on in 

 canals simply excavated in the substance of the body, without any outlet 

 for the discharge of superfluous matter," (although this cannot be said of 

 some of the higher types of Polygastrica, which, according to Ehrenberg, 

 have a straight intestinal tube with a double orifice, though the author 

 himself seems to throw doubt on the statement;) the nervous system 

 either perfectly diffused through the tissues, or but obscurely visible in 

 the most perfect species, and the sexes, with one exception, invariably 

 combined in the same individual, we arrive at a point in the scale of 

 animal development at which the nervous fibre becomes for the first time 

 distinct arid recognizable; the alimentary canal is visible as a separate and 

 distinct tube, and the ovigerous and impregnating sexual organs are found 

 to exist in different individuals. In the Gcelelmintha we find animals very 

 like the last family of the kingdom Acrita, but with a nervous system 

 distinctly developed, and muscular fibre in a rudimentary state is now also 

 recognisable. Their digestive apparatus consists of a simple tube running 

 from an sesophagus right through the body, without any apparent division 

 into stomach and intestine; and the animals are dioecious. 



The Bryozoa, or Ciliobrachiate Polyps, come next in order; and we 

 have many varieties of them on our own coasts, the commonest of which 

 is the Flustra Foliacea. These animals resemble somewhat the unciliated 



