THE PALEONTOLOGIC RECORD 145 



Another problem closely connected with that of the mode of loco- 

 motion is that of the origin of the organs of sense, and also upon this, 

 as far as the organs of seeing at least are concerned, the fossil inverte- 

 brates are able to throw some light, as in the trilobites and eurypterids. 



Another line of inquiry is that of the mode of nutrition as recog- 

 nizable by the appendages, and its influence upon the general structure. 

 Under this heading such interesting minor problems as that of the 

 origin of parasitism arise and may be solved, as indicated by a recent 

 publication as to the time of beginning, causes and gradual changes of 

 parasitism, to its very complex present conditions. 



Probably also the physiology of respiration will in time receive 

 important additions as far as the echinoderms, crustaceans, scorpions 

 and eurypterids are concerned. 



The widest scope, however, will have those problems that are con- 

 nected with the reactions of the organisms to their physical and chem- 

 ical surroundings. The invertebrate paleontologist meets forever, in 

 sight of the ever-changing faunules, the question, what exterior influ- 

 ences caused these changes? Often they can be directly recognized, as 

 in the dwarfed faunules of the Devonic pyritiferous Tully limestone or 

 of the bituminous Marcellus and Genesee shales or the eurypterid 

 faunas of the Salina lagoons. The systematic investigation of these 

 reactions through the series of formations is an inviting task. 



A special problem of singular interest connected with the reaction 

 of the organisms to the chemical surroundings is that of the composi- 

 tion of the shell of the invertebrates. There is good evidence for the 

 view that the shells were at first chitinous and that but gradually they 

 became calcareous or siliceous. This important question again is 

 intimately connected with that of the original composition of the ocean, 

 and this line of inquiry again leads us to the highly fascinating paleo- 

 physiological problem, lately so happily dealt with by Professor Lane, 

 as to the geological evidence on the original composition and origin 

 of the vital liquid, the original body temperature and the physiological 

 origin of the hard parts of the invertebrates in general. 



CONTRIBUTIONS TO MOEPHOLOGY FEOM 

 PALEONTOLOGY 



By Professor WILLIAM BULLOCK CLARK 



THE JOHNS HOPKINS UNIVERSITY 



OUR knowledge of the morphology both of the animal and plant 

 kingdoms has been largely extended by the work of the paleon- 

 tologist. Mention needs only to be made of the many species, genera 

 and families, even orders and classes, established solely for fossil forms 



