160 INTRODUCTION. 



maximum of development. All feathers do not possess a web (which 

 consists of branches from the shaft, termed barbs, each barb being fur- 

 nished with minute branches, or barbules) ; on the contrary, the quill- 

 feathers on the rudimentary wings of the Cassowary are simple spines, 

 closely resembling those of the Porcupine, except that they have a thick, 

 hollow barrel, or quill, at their base. 



ON SPECIES, HYBRIDS, AND VARIETIES; ON THE DURATION OF 

 LIFE, AND THE REPRODUCTION OF MAMMALIA. 



IT is important to establish, if possible, a clear definition of the term 

 species. Species are fixed and permanent forms of being, exhibiting, indeed, 

 certain modes of variation, of which they may be, more or less, susceptible ; 

 but maintaining, throughout those modifications, a sameness of structural 

 essentials, transmitted from generation to generation, and never lost by the 

 influence of causes, which, otherwise, produce obvious effects. It is by 

 keeping this principle in view, that we unhesitatingly decide upon the specific 

 distinction between fossil reliquia of extinct animals, and those now extant, 

 of near affinity : between the Mammoth, and the Asiatic Elephant ; 

 between the fossil species of Rhinoceros, and their living representatives. 

 Species are permanent. Varieties are either accidental, or the result of the 

 care and culture of Man. In the former case, they are of rare occurrence ; 

 in the latter, they perpetually exhibit a tendency to return to their original 

 condition. The difficulty of keeping up any particular breed of Pigeons 

 or Rabbits is well known ; the Sheep continually manifests a tendency 

 to resume the dark colour of the wild Mouflon ; black Sheep annoy 

 the farmer, by appearing in the midst of the most carefully-bred flock. 

 The dog, that most modified of all modified animals, requires care and 

 attention, in order to prevent its varieties from degenerating. Time alone 

 produces no effect in altering species : the mummies of animals found in 

 the catacombs of Egypt resemble their living descendants ; the represent - 

 ations of animals on the relics of Egyptian temples, or delineated on the 

 outer cases, in which, for from two to three thousand years, the remains of 

 Man have been preserved, are the faithful figures of existing species. No 

 animal, by a series of mystical transformations, can become an animal of a 

 different species. Lamarck, indeed, considered species as the result of cir- 

 cumstances, and not as original products of the creative fiat : he considered 

 the higher" animals, and also Man, to have attained their present state by 

 a gradual transition, through an indefinite period of time, from the lowest 

 form of life ; each race, as it advanced in elevation, transferring its assumed 

 characters to its posterity, to be by. them still farther modified, until the con- 



