672 



SCIENCE. 



[N. S. Vol. IV. No. 97. 



from the Class Perforata is mucli stronger, 

 the existing genera Nodosaria, Dentalina, 

 Textularia, Grammostomum, Vcdvulina and 

 Nummulina all occurring in the Carbon- 

 iferous, together with the new genera 

 Archcediscus (?) and Fusulina. 



I omit reference to the much-disputed 

 Eozoon from the Laurentian rocks far be- 

 low the horizon, which, for the purpose of 

 this address, I am considering as the lowest 

 fossiliferous stratum. "We are looking for- 

 ward to the new light which will be thrown 

 upon this form in the communication of its 

 veteran defender. Sir William Dawson, 

 whom we are all glad to welcome. 



Passing the Eadiolaria, with delicate 

 skeletons less suited for fossilization, and 

 largely pelagic and, therefore, less likely to 

 reach the strata laid down along the fringes 

 of the continental areas, the next Phylum 

 which is found in a fossil state is that of the 

 Porifera, including the sponges, and di- 

 vided into two classes, the Calcispongise and 

 Silicospongise. Although the fossilization 

 of sponges is in many cases very incom- 

 plete, distinctly recognizable traces can be 

 made out in a large number of strata. 

 From these we know that representatives 

 of all the groups of both classes (except the 

 Halisarcidse, which have no hard parts) 

 occurred in the Silurian, Devonian and Car- 

 boniferous systems. The whole Phylum is 

 an example of long persistence with ex- 

 tremely little change. And the same is 

 true of the ISTematophora ; new groups, in- 

 deed, come in, sometimes extremely rich in 

 species, such as the Palaeozoic Eugose corals 

 and Graptolites ; but they existed side by 

 side with representatives of existing groups, 

 and they are not in themselves primitive or 

 ancestral. A study of the immensely nu- 

 merous fossil corals reveals no advance in 

 organization, while researches into the 

 structure of existing Alcyonaria and Hydro- 

 corallina have led to the interpretation of 

 certain Palseozoic forms which were previ- 



ously obscure, and the conclusion that they 

 find their place close beside the living 

 species. 



All available evidence points to the ex- 

 treme slowness of progressive evolutionary 

 changes in the Coelenterate Phyla, although 

 the Protozoa, if we may judge by the Ee- 

 ticularia (Foraminifera), are even mor& 

 conservative. 



When we consider, later on, the five Coelo- 

 mate Phyla which occur fossil, we shall 

 find that the progressive changes were 

 slower and, indeed, hardly appreciable in the 

 two lower and less complex Phyla, viz : the 

 Echinoderma and Gephyrea, as compared 

 with the Mollusca, Appendiculata and Yer- 

 tebrata. 



Within these latter Phyla we have evi- 

 dence for the evolution of higher groups 

 presenting a more or less marked advance 

 in organization. And not only is the rata 

 of development more rapid in the highest 

 Phyla of the animal kingdom, but it ap- 

 pears to be most rapid when dealing with 

 the highest animal tissue, the central 

 nervous system. The chief, and doubtless 

 the most significant, difference between the 

 early Tertiary mammals and those which 

 succeeded them, between the Secondary and 

 Tertiary reptiles, between man and the 

 mammals most nearly allied to him, is a dif- 

 ference in the size of the brain. In all these 

 cases an enormous increase in this, the 

 dominant tissue of the body, has taken, 

 place in a time which, geologically speak- 

 ing, is very brief. 



When treating, later on, of the evolu- 

 tion which has taken place within the 

 Phyla, further details upon this subject 

 will be given, although in this, as in other 

 cases, the time at our disposal demands 

 that the exposition of evidence must largely 

 yield to an exposition of the conclusions 

 which follow from its study. And undoubt- 

 edly a study of all the available evidence 

 points to the conclusion that in the lower 



