On Outgrowths and Appendages 45 



pads, no tusks. The canine teeth in the lower jaw, which look 

 like incisors, are much specialised in being cleft or notched. 



It is a case of competitive growth and the tubers win. 

 After a time the plant will in the course of inheritance learn 

 that it is useless to produce flowers, will give up the attempt ; 

 indeed, many varieties have already done so to a considerable 

 extent. 



No better instance could perhaps be given of the law 

 which goes through all animated Nature that activity is 

 almost essential to continuance of life, whether in individuals 

 or their parts. 



The Oldest Fossils (Lingula). — It is a noteworthy fact that these, 

 the oldest fossil animals known, belong to species by no means low 

 in the scale. Yet every trace of the many millions which must have 

 preceded them, and have gradually led up to their development, have 

 perished. The period of time which must have elapsed subsequent 

 to the advent of life upon the planet and the development of the 

 lingula mollusc was probably quite as long as that which has passed 

 since the lingula left its shell in the mud of the Portmadoc slate. 

 The oldest fossils which are known are found in the lower Cambrian 

 rocks. They are small oval shells, which were, during life, the pro- 

 tection of small soft-bodied sea animals of highly complex structure : 

 they had red blood. Their descendants are still found in great 

 numbers burrowing in sand on the shores of tropical oceans. They 

 have received the name of Lingula, and have in turn conferred that 

 name on certain hard rocks in which their shells occur in abundance, 

 the " Lingula flags " of Wales (Ra\ Lankester). 



Huge Shark's Teeth. — Ray Lankester figures, in his interesting 

 lectures on extinct animals from which we have quoted the above a 

 gigantic shark's tooth. It is that of the Carharodon megalodon, and 

 is three times the length of the tooth of any living shark. Specimens 

 of this fossil tooth of smaller dimensions are common, and one should 

 be found in every museum. They are obtained from the bone bed 

 of the Red Crag at Felixstowe, but were not originally deposited in 

 it. Many of them have fragments of a yet older sandstone adhering 

 to them. Lankester calculates that his shark was 100 feet long. 



