144 HISTOEY OF THE WORKS OF CUVIER. 



he called by the same name. In like manner, since the organization of the 

 fliollusks had become known, it could no longer be pretended that there were 

 not between these animals many more differences than between the animals of 

 a single class of vertebrata ; and consequently again, since there was no parity 

 between the beings comprised in these two divisions, iXiavc wasno parity of division, 

 and there ought, therefore, to be no parit}' of name. 



But this was not all. By still comparing the structures, and taking them for 

 a guide, it was not less evident that the crustaceans united to the insects, and these 

 two groups to that of the tcorms with red hlood, or annelids, formed by their 

 importance, by the number of their species, by their structures so essentially di verse, 

 a third division, similar either to that of the vertebi'ata or to that of the moUusks ; 

 and that all other animals, imited thenceforth under the name of zooplujtcs, formed 

 a fourth division similar to each of the three preceding. Considered under this 

 new point of view the animal kingdom presents therefore four grand divisions or 

 branches : that of the verlchrata, that of the molluscas, that of the articidata, 

 and that of the zoophyta. 



Each of these divisions is formed on a particular and distinct plan ; that is to 

 say, one which cannot be reduced to that of the others ; and they are all like 

 one another in being of the same order ; that is to say, that the beings they include 

 present, in their structure, similar or equivalent resemblances or differences. 

 Thus the vertebrata have their plan, the mollusks have theirs, the articulata, 

 the zoophytes have theirs, and all these plans are alike circumscribed ; that is to 

 say, that no shading, no intermediary, no lien, can make them pass from one to 

 the other without a rupture, without a saltus. A kind of circumvallation separates 

 them. We can pass by modifications more or less graduated from man, con- 

 sidered in his organization to the other mammifers, from mammifers to birds, 

 from birds to reptiles, from reptiles to fishes ; but from fishes to mollusks, from 

 mollusks to articulata, from articulata to zoophytes, there is no longer any grad- 

 ation or natural transition. All at once the plan changes and a new form shows 

 itself; but taken in itself this new form, this new type, is equally constant, preva- 

 lent, uniform ; all the mollusks repeat as exactly their own type as the vertebrata, 

 the articulata, the zoophytes, repeat theirs. Thus, in the immense chain of the 

 animal kingdom there are four great forms, four grand types, and there are but 

 foul". 



This capital fact is equally worthy of note whether we consider it as showing 

 that, with the exception of a few secondary modifications, all animals enter exactly 

 into one or the other of these great forms, or whether Ave consider it as showing 

 that between each of these great forms there is no shading, no giTidation, no 

 intermediate form. The vertebrata alone have a spinal marrow, a long medullary 

 cone, into the sides of which enter the nerves, and which is enlarged at its ante- 

 rior extremity to form the encephalon; they alone have a double nervous system, 

 that of the spinal marrow and that of the great s^nnpathetic ; they alone have a 

 canal composed of bony or cartilaginous vertebrse. But all of them have this 

 spinal marrow, this great sympathetic, these vertebras; all have senses to the 

 number of five, horizontal ja\\s to the number of two, red blood, a muscular heart, 

 a SA'stem of chylifenjus and absorbent vessels, a liver, a spleen, a pancreas, kid- 

 neys, &c. In a word, the more we examine their whole organization the more 

 resemblances do we discover. 



But the more differences do we also find as regards the other emhranchments. 

 The mollushs, for example, have also a brain, though infinitely reduced ; but 

 they have no spinal marrow, and consequently no vertebrte ; they have no great 

 sympathetic, and their single nervous system, instead of being placed above the 

 digestive canal, as in the vertebrate animals, is always placed, with the cxcepticm 

 of the single ganglion which represents the brain, below that canal, being con- 

 signed to the viscera; in fine, the_y have neither a true skeleton nor absorl)ent 

 vessels, nor spleen, nor pancreas, nor veyia-porta, nor kidneys ; the organ of smell 



