THE EVOLUTION OF ORGANIC TYPES IN TIME. 105 



of a sufficient number of such transitional forms, and the insufficient 

 connection between such as are known to exist, may doubtless be 

 in part explained by the known " imperfection of the geological 

 record " ; but this does not appear to offer an adequate solution of 

 the difficulty. The theory of " the origin of species by means of 

 natural selection," as elaborated by the master-mind of Darwin, 

 constitutes, nevertheless, an invaluable, indeed an indispensable, 

 guide in all branches of palaeontological research. 



LITERATURE. 



[With regard to the subjects dealt with in the introductory portion of 

 this work, the following are some of the original sources of information to 

 which the student may have recourse. It is to be remembered, however, 

 in the case of this, as of subsequent bibliographical lists of a similar char- 

 acter, that nothing more has been attempted than to give a selection of 

 the more important original memoirs.] 



1. " Anniversary Address to the Geological Society of London." (Min- 



ute Structure and Chemical Composition of the Calcareous Skele- 

 ton of Invertebrates ; Structure of Limestones, &c.) 1879. Sorby. 



2. " Anniversary Address to the Geological Society of London." (Ge- 



ological Contemporaneity and Persistent Types of Life.) 1862. 

 Huxley. 



3. " Address to the Geological Section of the British Association for the 



Advancement of Science." (Homotaxis.) 1884. Blanford. 



4. " Relative Ages of American and English Fossil Floras." ' Geological 



Magazine,' 1884, p. 496. J. Starkie Gardner. 



5. " Homotaxis and Contemporaneity." ' Geological Magazine,' 1886, 



p. 293. Oldham. 



6. " The Application of Biology to Geological History." ' Proc. Biolog- 



ical Soc. of Washington/ 1886. C. A. White. 



7. " The Inter-relation of Contemporaneous Fossil Faunas and Floras." 



' Amer. Journ. Sci. and Arts,' vol. xxxiii., p. 364, 1887. C. A. 

 White. 



8. " The Origin of Species by means of Natural Selection." (Chapters 



x. and xi., on " the Imperfection of the Geological Record," and 

 on " the Geological Succession of Organic Beings.") Sixth Edition, 

 1872. Darwin. 



9. "Defense des Colonies." 1865 an d 1870. Barrande. 



10. " The Pre-Devonian Rocks of Bohemia." (The " Colonies " of Bar- 

 rande.) 'Quart. Journ. Geol. Soc.,' vol. xxxvi., 1880. J. E. Marr. 



n. "On the Nomenclature, Origin, and Distribution of Deep-sea De- 

 posits." ' Proc. Roy. Soc. Edin.,' 1884. John Murray and A. 

 Renard. 



12. "Report on the Deep-sea Deposits." 'Narrative of the Cruise of 



H.M.S. Challenger,' vol. ii., Part ii., 1885. 



13. " The Geographical and Geological Distribution of Animals." 1887. 



Heilprin. 



14. " Ueber klimatische Zonen wahrend der Jura- und Kreide-Zeit.' 



' Denkschriften der kais. Akad. der Wiss.' Vienna. 1883. Neu- 

 mayr. 



15. " Les Ancetres de nos Animaux dans les Temps Geologiques." 1888. 



Gaudrv. 



