i44 THE POPULAR SCIENCE MONTHLY 



what have undergone modifications due to functional changes. It is 

 obvious that here invertebrate paleontology is in a position to answer a 

 host of questions that could not be successfully approached by compar- 

 ative anatomy of recent forms, by the direct observation of successive 

 changes. Its methods of investigation have already been applied with 

 wonderful success to large parts of our Paleozoic crinoids, brachiopods, 

 bryozoans and cephalopods. And I do not doubt that the time has 

 come when the preliminary stage of mere description of fossils is passed, 

 and a monographic treatment of each class that would fully enter into 

 the comparative anatomy of all structures preserved, could be profitably 

 undertaken. 



It is only by this work that paleontology can hope to make those 

 contributions to philosophical anatomy in revealing the causes of the 

 different structures which it is especially fitted and called upon to 

 furnish by its ability to study the gradual development of the struc- 

 tures. Wherever a class of fossils has been thus thoroughly treated, it 

 has given a fruitful crop of new hypotheses and principles, as is in- 

 stanced by Hyatt's investigation of the fossil cephalopods. Most 

 classes, and especially the corals, echinoids and trilobites, await such 

 treatment by competent investigators. 



Since physiology is that branch of biology that treats of the laws of 

 phenomena of living organisms, it might seem hopeless to expect any 

 information from the fossil world. This is apparently the more true 

 in regard to the invertebrates, since a special physiology exists thus far 

 only for men and the higher invertebrates and the recent invertebrates 

 are largely a virgin field. For this reason also, only the most general 

 foundations of comparative physiology have been laid, and an inverte- 

 brate fossil physiology would get as yet but little support from that 

 side. Moreover, the main source of exact information in recent physi- 

 ology is the experimental method, and this is wholly inapplicable to 

 the fossil world. 



And yet it seems to us that the empiric method upon which physi- 

 ology has so long flourished promises also rich fruit in paleontology. 

 I can do no more now than briefly mention the problems that most 

 readily suggest themselves here. Invertebrate paleontology will be 

 especially competent to furnish contributions to the mechanics of 

 physiology by throwing light on the development of the means and 

 modes of locomotion. In connection with this problem invertebrate 

 paleontology also shows most clearly the deep-reaching influence of 

 secondary fixation on the structure of the organism, as in the case of 

 the strange Richtliofenia among the brachiopods and the Kudistae 

 among the lamellibranchs. It can not fail that the progress in recent 

 invertebrate physiology will stimulate inquiry into the physiology of 

 the fossils; and further that, as invertebrate fossil anatomy progresses, 

 the data for such inquiry will also come forth. 



