33 



in areas now geographically separated ; and its universal dis- 

 semination rendering it easy of collection and study." 



Even among Lap worth's papers it is difficult to find another 

 which is such a perfect masterpiece of knowledge, research, and 

 presentation ; and that is praise indeed. It is not merely a com- 

 plete vindication of the character of the graptolite as a zone fossil, 

 and a final justification of the author's method of work. It is a 

 thoroughly reliable study of the geological relations of the 

 order, and a store of information mined, refined, and tested to 

 breaking point, of the steel-like links which he forged to bind 

 together the lower palaeozoic horizons throughout the world. 



4. The Life of the Graptolites. 



By his study of the graptolites in the field and of their nearest 

 living representatives, Lapworth had gradually built up for himself 

 a picture of the living graptolite, its life story, its colonial history, 

 and the conditions and methods which had determined its 

 survival, evolution, and distribution. This he contributed in 

 German, ' Die Lebensweise der Graptolithen,' to a paper by Dr. 

 Johannes Walther, published in the Zeitschrift der deutschen 

 geologischen Gesellschaft in 1897 (54). 



The earliest graptolites, the Cladophora, seem to have grown 

 upright, attached to stones and heavy objects on the sea bed. 

 With the incoming of Dictyonema and the rest of the Rhabdophora. 

 there is attachment by a thread to floating organisms, probably 

 sea-weeds of Sargasso type. In this way the graptolites secured 

 an ocean-wide distribution by currents and winds, and there is 

 explained the presence of their fossil remains in such abundance 

 in deep sea muds, the carbonaceous matter of which is 

 provided by the weeds, and at the same time the reason 

 for the great areas covered by the graptolite zones, and the 

 value of graptolites, exceeding that of any other pelagic 

 organism, as time zone indices. Light is thrown on the biological 

 evolution of the order, on the branching of the colonies, on the 

 gradual simplification, and on the development of the thecae for 

 obtaining larger supplies of food and better exposure to sun -light. 



From this also follows what he often pointed out the signi- 

 ficance of the plenitude of graptolites when their main enemies 

 were no better equipped than trilobites, and their rapid extinction 

 when fishes made their appearance on the scene. 



5. Monograph of British Graptolites (62). 



It was only fitting that this work should culminate in the 

 publication of a complete Monograph on the British Graptolites ; 

 but the time and facilities for this, though it was often contem- 

 plated and preparations were continually being made for it, could 



