pound rapidity by the force of spontaneous fission. It was a favorite pro- 

 verb with Linnaeus " Natura non facit saltum" — Nature makes no leap — and 

 if the great author of the ' Systema Naturae ' felt the force of this axiom in 

 a time when the knowledge of species was extremely limited, how much 

 stronger may the truth of it be now demonstrated when so many of the links 

 then wanting in the chain of affinity have been revealed to observation. 

 Every day we are invited to the contemplation of some new form, some new 

 contribution to the general harmony of the series ; and it is this inexhaus- 

 tible source of novelty that imparts such a charm to the study. There is 

 a modifying force in nature, that seems ever labouring to increase the par- 

 ticipation of characters that were hitherto unapproachable. She delights in 

 confounding the systematist ; — she does not choose to be defined. 



Linnams lived in a time when the researches into the comparative organi- 

 zation of the inferior animals were not very profound. The characters dis- 

 tinguished by the modern Aristotle exhibit, frequently, a violation of natural 

 affinity ; whilst they are too often artificial and void of equivalency. As 

 soon as the immortal Cuvier began to look into the nervous and other com- 

 plicated portions of the animal frame, the results proved to be such as to 

 materially affect the prevailing method of classification. The physiological 

 generalizations deduced from this new field of enquiry presented sounder 

 combinations of character ; and we are indebted to as great a comparative 

 anatomist of our own day*, for having matured and added to the investiga- 

 tions of his illustrious predecessor. 



Cuvier did not, however, enter so minutely into the discrimination of 

 species, as did his contemporary Lamarck ; the first distinction which the 

 great author of the ' Histoire des animaux sans vertebres ' recognised in 

 the primary distribution of the Animal Kingdom, was that of the higher 

 orders, which include Mammals, Birds, Reptiles, and Fishes, being furnished 

 with a vertebral column supporting an internal frame or skeleton, whilst 

 the remainder are destitute of any ; and he divided accordingly the Vertebrate 

 from the Invertebrate. " Now it will be observed ", says Professor Owen, 

 " that the invertebrate animals are here grouped together by a negative cha- 

 racter, and I know not any instance where such a character has been em- 

 ployed in zoology in which very differeidy organized species have not been 

 associated together. What indeed can be predicated in common of the 

 Snail, the Bee, and the Polype, than that they are animals and have no ver- 

 tebral columns, and the like negations?" f 



Although Lamarck, therefore, may be followed in the detail of classifica- 

 tion, it is necessary for the primary distribution to follow the method adopted 

 by Cuvier and Owen, who divide the Animal Kingdom into four- Sub-king- 

 doms, the Vertebrata, the Mollusca, the Articulata, and the Eadiata ; 



* Owen. t Hunterian Lectures 1S44. 



