Professor J. E. Marr — Address. 477 



but recent researches amongst various groups of fossil organisms have 

 further illustrated the danger of theorizing upon insufficient data, especially 

 suggestive being the discovery of closely similar forms which were formerly 

 considered to be much more nearly related than now proves to be the 

 case. Thus Dr. Mojsisovics l has shown that Ammonites once referred to 

 the same species are specifically distinct, though their hard parts have 

 acquired similar structures, sometimes contemporaneously, sometimes at 

 different times ; and Mr. S. S. Buckman 2 has observed the same thing, 

 which he speaks of as " heterogenetic homceomorphy " in the case of 

 certain brachiopods ; whilst Professor H. A. Nicholson and 1 3 have given 

 reasons for supposing that such heterogenetic homceomorphy, in the case 

 of the graptolites, has sometimes caused the inclusion in one genus of 

 forms which have arisen from two distinct genera. As the result of 

 careful work, dangers of the nature here suggested will be avoided, and 

 our chances of indicating lines of descent correctly will be much increased. 

 It must be remembered that, however plausible the lines of descent 

 indicated by students of recent forms may be, the actual links in the 

 chains can only be discovered by examination of the rocks, and it is 

 greatly to be desired that more of our geologists, who have had a thorough 

 training in the field, should receive in addition one as thorough in the 

 zoological laboratory. Shall I be forgiven if I venture on the opinion that 

 a certain suspicion which some of my zoological fellow-countrymen have 

 of geological methods, is due to their comparative ignorance of palaeontology, 

 and that it is as important for them to obtain some knowledge of the 

 principles of geology as it is for the stratigraphical palaeontologist to study 

 the soft parts of creatures whose relatives he finds in the stratified rocks ? 

 The main lines along which the organisms of some of the larger groups 

 have been developed, have already been indicated by several palaeontologists, 

 and detailed work has been carried out in several cases. As examples, let 

 me allude to the trilobites, of which a satisfactory natural classification 

 was outlined by the great Barrande in those volumes of his monumental 

 work which deal with the fossils of this order, whilst further indication of 

 their natural inter-relationships has been furnished by Messrs. C. D. 

 Walcott, G. F. Matthew, and others ; to the graptolites, whose relation- 

 ships have been largely worked out by Professor C. Lapworth, facile 

 princeps amongst students of the Graptolitoidea, to whom we look for 

 a full account of the phylogeny of the group ; to the brachiopods, which 

 have been so ably treated by Dr. C. E. Beecher, 1 largely from a study 

 of recent forms, but also after careful study of those preserved in the fossil 

 state ; and to the echinoids and lamellibranchs, whose history is being 

 extensively elucidated by Dr. R. T. Jackson, 5 by methods somewhat 

 similar to those pursued by Dr. Beecher. I might give other instances, 6 

 but have chosen some striking ones, four of which especially illustrate 

 the great advances which are being made in the study of the palaeontology 

 of the invertebrates by our American brethren. 



1 E. Mojsisovics, Abliandl. der k. k. geol. Eeichsanst., vol. vi (1893). 



2 S. S. buckman, Quart. Jouru. Geol. Soc, vol. li (1895), p. 4-56. 



3 H. A. Nicholson and J. E. Marr, Geol. Mag., Dec. 4, Vol. II (1895), p. 531. 



4 C. E. Beecher, "Development of the Brachiopoda " : Amer. Journ. Sci., ser. iii, 

 vol. xli (1891). p. 343, and vol. xliv (1892), p. 133. 



5 R. T. Jackson, " Phylogeny of the Pelecypoda," Mem. Boston Soc. Nat. Hist., 

 vol. iv (1890), p. 277 ; and " Studies of Palseechinoidea," Bull. Geol. Soc. Amer., 

 vol. vii (1896), p. 171. 



6 E.g. the following papers treating of the Cephalopoda : A. Hyatt, " Genesis 

 of the Arietidae," Smithsonian Contributions, vol. xxvi (1889) ; M. Neumayr, Jura- 

 Studien I, " Ueber Phylloceraten," Jahrb. der k. k. Geol. Eeichsanst, vol. xxi 

 (1871), p. 297; L. "Wurtenberger, " Studien iiher die Stammesgeschichte der 

 Ammoniten," Leipzig, 1880; S. S. Buckman, "A Monograph of the Inferior 

 Oolite Ammonites of the British Islands," 1887, Monogr. Palajoutographical Soc. 



