Chap. I. EARLIEST TYPES OF ANIMALS. 25 



periods, iiiid ns IIrmt order of appiirition corresponds to the various degrees of com- 

 plication in their striieturo, and fcn-nis natural series closely linked together, this 

 natural gradation must have been contemplated from the very beginning. There 

 can l)e the less doubt u])i)U this ])oint, as man, who comes last, closes in his own 

 cycle a series, the gradation of which points from the very beginning to him as its 

 liist term. T think it can be shown by anatomical evidence that man is not only 

 the last and highest among the living beings, for the present period, but that he is 

 the last term of a series bej-ond which there is no material progress pos.sible upon 

 the plan upon which the whole animal kingdom is constructed, and that the only 

 improvement we may look to upon earth, for the future, must consist in the develop- 

 ment of man's intellectual and moral faculties.^ 



The que.stion has been raised of late how far the oldest fossils known may truly 

 be the remains of the first inhabitants of our globe. No doubt extensive tracts of 

 fossiliferous rocks have been intensely altered by plutonic agencies, and their organic 

 contents so entirely destroyed, and the rocks themselves so deeply metamorpho.sed, 

 that they resemble now more closely eruptive rocks even than stratified deposits. 

 Such changes have taken place again and again up to comparatively recent period.s, 

 and upon a very large scale. Yet there are entire continents. North America, for 

 instance, in which the palaeozoic rocks have undergone little, if any, alteration, and 

 where the remains of the earliest representatives of the animal and vegetable king- 

 doms are as well preserv^ed as in later formations. In such deposits the eAadence is 

 satisfactory that a variety of animals belonging to different classes of the great 

 branches of the animal kingdom have existed simultaneously from the beginning ; so 

 that the assumption of a successive introduction of these types upon earth is flatly 

 contradicted by well established and well known facts.^ Moreover, the remains found 

 in the oldest deposits, are everywhere closely allied to one another. In Russia, in 

 Sweden, in Bohemia, and in various other parts of the world, where these oldest 

 formations have been altered upon a more or less extensive scale, as well as in 

 North America, where they have undergone little or no change, they present the 

 same general character, that close corre.spondence in their structure and in the 

 combination of their ilxmilies, which shows them to have belonged to contempora- 

 neous fiiuna). It would, therefore, seem that even where metamorphic rocks prevail, 

 the traces of the earliest inhabitants of this globe have not l)een entirely obliterated. 



' AcASsiz, (L.,) An Introduction to tlic Study Nuinboi- of Animals in Geolon;ical Timos, Amcr. 



of Natural IILstory, New York, 1847, 8vo. p. 57. Journ. of Science and Arts, 2d sen., vol. 17, 18J4, 



* Agassiz, (L.,) Tiio rriniitive Diversity and p. HW. 



4 



