72 CATTLE-BREEDING. 



tain itself. The early forms of this mollusk 

 inhabited a slender tube often of very great 

 length, as for example the orthoceratite, which 

 is a common Silurian fossil. In later times 

 the more highly developed species were closely 

 coiled, the highest of all being the still existing 

 but rare "pearly nautilus," commonly known 

 as the "paper sailor." For a great period the 

 conditions seemed highly favorable to this fam- 

 ily, and many beautiful species are preserved 

 in our rocks. But a time came when the world 

 had ceased to smile on them. The beautiful 

 spirals then began to uncoil; some straightened 

 out almost to the straight tube of the first an- 

 cestral type, and from this to the close coil al- 

 most every imaginable modification has been 

 found. It was a brave fight plainly enough, 

 but a vain struggle against an unkind fate. 



It logically follows that such variations as 

 are produced by an effort at adaptation to new 

 surroundings would be likely to reproduce 

 themselves upon the descendants of the animal 

 in which it exists. In the variations of the 

 class first treated of there is no such marked 

 logical basis for persistence, since when bred 

 back to animals of the ordinary form of the 

 species the whole force of inheritance would 

 militate to eradicate it. But even in these 

 cases the malformation or other variation 

 shows oftentimes a prepotency over the nor- 



