EVIDENCE FROM PALAEONTOLOGY. 163 



But there also exists, at considerable depths and on the bottom 

 of the sea, a rich and varied animal life. This has only lately been 

 brought to our knowledge principally by the deep-sea explorations 

 from North America, Scandinavia, and England. In place of that 

 want of animal life which we should on a priori grounds expect 

 to find, we see that numerous lowly organised animals of the 

 most different groups are able to exist even at the greatest 

 depths. Besides the lowest sarcode animals of the Foraminifera 

 (Grlobigerina ooze), we find especially silicious sponges, certain corals, 

 Echinoderms, and Crustacea* The representatives of the latter 

 are in part of low type, but gigantic, and many of them blind. 

 It is also a fact of more than ordinary interest, as showing the 

 continuity of living creatures from successive geological forma- 

 tions up to the present time, that the deep sea animals are allied 

 to ancient types which occur in Mesozoic formations, especially in 

 chalk. 



Evidence from Palaeontology. The results of geological and 

 palceontological inquiry give us a third great series of facts in 

 support of the theory of slow alterations of species and the 

 gradual development of genera, families, orders, etc. The firm 

 crust of our earth is formed of numerous and enormous rock 

 strata, which have been deposited in a definite series by water in 

 course of time, and also of the so-called volcanic or plutonic rocks, 

 masses which have been forcibly ejected from the molten interior 

 of the earth. The former or sedimentary deposits, which have under- 

 gone numerous alterations in the originally horizontal arrangement 

 of their strata -as well as in the petrographical condition of their 

 rocks, contain a quantity of the fossilized remains of former plants 

 and animals which have become buried in them, and thus afford an 

 historical record of a rich fauna and flora which existed during the 

 earlier periods of the earth's development. Although these so-called 

 fossils have made us acquainted with a very considerable number of 

 ancient organisms presenting great diversity of form, yet they only 

 constitute a very small portion of the enormous quantity of living 

 beings which have at all times existed upon the earth. They 

 suffice, however, to teach us that a different fauna and flora existed 

 at the time when each individual deposit was being formed, and that 



* Compare Wyville Thomson, " The depths of the sea. An account of the 

 general results of the dredging cruizes of the Porcupine and Lightning, during 

 the summer months of 1868, 1869, 1870." London, 1873. Also the results of the 

 Challenger expedition 1874-1876. 



