50 BIOLOGICAL LECTURES. 



adds to the confusion, the very completeness of the record 

 increasing the difficulty of its interpretation. 



(2) A second drawback to the palaeontological method of 

 inquiry lies in the incomplete preservation of those organisms 

 which are fossilized. Of plants we find, for the most part, 

 only scattered leaves, rarely the reproductive organs, stems, or 

 roots, and often the proper association of the various parts 

 requires the strenuous labor of years. Of animals, except 

 under exceedingly rare circumstances, only the hard parts, 

 teeth, bones, shells, and the like, are preserved, and in the case 

 of vertebrates how seldom is even the skeleton completely 

 recovered ! As in plants, the association of the various parts 

 of a single skeleton may require the long-continued and 

 laborious efforts of many workers. Extraordinary blunders 

 have sometimes been committed in this work. In the remark- 

 able genus Chalicotherium the skull was at first referred to one 

 mammalian order and the feet to another, and Forsyth-Major's 

 suggestion that they all belonged together was received with 

 incredulity. Of the even more curious Agriochcerus the head 

 was ascribed to one order, the fore-leg to a second, and the 

 hind-foot to a third. 



The utterly false notion, which nothing seems able to eradi- 

 cate, that the palaeontologist can readily restore an extinct 

 type from a single bone or tooth, ought to receive its quietus 

 from such examples, though of course it will not. It is 

 equivalent to saying that we have nothing to learn from the 

 fossils, and that all possible types of structure are exemplified 

 in the living world. 



On account of this incompleteness of preservation we cannot 

 learn much that we wish to know of the structure of extinct 

 organisms. The nervous, vascular, muscular, and alimentary 

 systems are entirely lost and can be inferred only from indirect 

 and often insufficient evidence. Were the pearly nautilus 

 extinct, our notions of the anatomy of the tetrabranchiate 

 cephalopods would be very much astray, and in the cases of 

 several groups of fossils we are quite unable to interpret the 

 structure from what remains. 



(3) A third difficulty in the way of a truly morphological 



