RELATION OF BIOLOGY TO GEOLOGICAL INVESTIGATION. 251 



I. THE CHARACTER AND ORIGIN OF FOSSIL REMAINS. 



In prosecuting the study of the fossil remains of animals and plants, 

 the investigator may have either one or the other of its two leading 

 objects in view, but each being so closely related to the other it is al- 

 ways essential that they should be pursued with direct relation to each 

 other. In the first case, the leading object to be attained is the exten- 

 sion of our knowledge of the animal and vegetable kingdoms far beyond 

 that which may be acquired by the study of living animals and plants, 

 and in the second case it is to apply that knowledge to the study of 

 structural and systematic geology. The object in the first case is 

 purely paleontologieal; in the second it is not only to acquire paleonto- 

 logical knowledge, but to apply it to various branches of geological in- 

 vestigation. 



This essay, like the others which follow it, is written with imme- 

 diate reference to the latter object, but the facts presented in it are of 

 equal importance to the former. My principal purpo.se in writing it 

 is the presentation of such facts as indicate the true significance and 

 value of fossil remains in geological investigation that the references 

 which are made in the following chapters may be the better understood. 

 While I endeavor to point out clearly those facts which show the 

 paramount value of fossil remains in geological investigation, I do 

 not hesitate to also point out their imperfection as representatives of 

 formerly existing faunas and floras as well as of separate members of 

 the same. This candid treatment of the subject is not only proper in 

 itself, but it is necessary in view of the fact that in the following essays 

 I oppose certain views which are shown by geological literature to 

 be held by many authors, especially those which indicate an under- 

 estimation of the value of all fossil remains on the one hand and the 

 relative overestimation of the value of certain kinds on the other. A 

 large part of this essay is of the most elementary character, but the 

 necessity for having such elementary matter at hand for reference has 

 already been pointed out, and it will further appear in the following- 

 essays. 



The substance of the bodies of animals considered with reference to 

 the subject of fossili/ation may conveniently be divided into soft and 

 hard parts. The soft parts are those constituting the organs by which 

 the physiological functions of the body are performed, together with 

 their connecting tissues, while the hard parts are skeletal and protec- 

 tive in their character. Some animals are destitute of either skeletal 

 or hard protective parts, and their bodies are therefore wholly soft or 

 fleshy. 



The soft parts of animals are always so soon and so completely de- 

 composed after death that they are never really fossilized, but in rare 



