296 Professor Charles Lapworth, LL.D., F.R.8. 



the world, so far as was then possible, was analysed, tabulated, and 

 described, and the inference established that the graptolite was as 

 reliable as the ammonite for a working stratigraphical index. 



Some yeai's elapsed before these conclusions were accepted in their 

 entirety, except by his friends and fellow-workers in Scandinavia, 

 but gradually his methods were taken up by first one and then 

 another of the younger men in Britain and abroad, until, eventually, 

 students of Palaeozoic rocks in all parts were sending Lapworth 

 graptolites for identification, and numerous jDapei'S and appendices 

 to papers, containing descriptions of new species and identifications 

 of old ones, were published (1875, 1877, 1881). St. David's, County 

 Down, Central Wales, and many other British districts soon yielded 

 graptolites in sufficient quantity to enable the rock-horizons to be 

 ascertained, and though the results sometimes conflicted with the 

 apparent stratigraphy, that was only so much the worse for 

 appearances and so much the better for facts. From foreign 

 countries and from the Colonies specimens came in for identi- 

 fication and as tests of the mapping. Led insensibly thereto by 

 their own discoveries, palaeontologists fell into the habit of similarly 

 classifying their fossils and employing them zonally, so that now 

 the despised graptolite of thirty years ago has become universally 

 accepted as the guide to the zonal order of the older fossiliferous 

 rocks. 



The Upland work demonstrated that graptolites had not been 

 standing still while all the Silurian rocks were being deposited, 

 but that there had been continual variation, modification, and 

 evolution. This, with the material subsequently accumulated, 

 bearing on the life-history and habitats of the group and the 

 probable causes to which their evolution was due, enabled Professor 

 Lapworth to contribute to a paper by Walther an important com- 

 munication on the " Mode of Life of the Graptolites" (1897), in which 

 he advanced the theory that whilst the earliest and dendroid graptolites 

 stood upright in shallow shore water, the later and more typical 

 forms (Rhabdophora) hung suspended from floating sargasso-like 

 seaweeds, so that they were drifted over the sea- waters as ' pseudo- 

 plankton ' by currents, and their skeletons thus distributed more or 

 less all over the sea-bed. This gave origin to the wide distribution 

 of graptolite zones, and also, in all probability, was the actuating 

 cause of the morphological evolution of the families and genera of 

 Rhabdophora, as well as the explanation of their abundance in black 

 carbonaceous shales. 



Later on Dr. Lapworth undertook the task of describing the 

 British graptolites for the Palseontographical Society, and devoted 

 a large amount of time to the correct drawing and illustrating of the 

 fossils. Numerous experiments in the reproduction of illustrations 

 were tried and are still being tried, and a new form of microscope 

 (the Lapworth-Parkes) was worked out, by which even large 

 specimens can be drawn in great detail, and under such conditions 

 of lighting that no important point of structure is omitted, the main 

 purpose being to present the object as like nature as possible without 



