LIFE OF FLOWER 121 



have been developed unless the animal required them. 

 For what could such powerful muscles be required ? 

 Most certainly not for slicing fruits or succulent roots 

 and bulbs, nor would they be required even for the 

 slicing of fleshy fibres. Temporal muscles are chiefly 

 used apparently for closing the jaws more or less forcibly 

 from the open position, while for the more complicated 

 movements of mastication it is the masseter and pterygoid 

 muscles that are chiefly used. Hence in all carnivorous 

 animals the temporals are largely developed and the 

 n:asseters more feebly, because the killing process 

 requires a very forcible closing of the jaws, and the 

 work to be done by the premolars and molars is com- 

 paratively little. In herbivorous animals the conditions 

 are reversed. The jaws are here rarely required to be 

 opened widely or to be closed with any great force, 

 while a very large amount of grinding work has to be 

 done ; hence the temporals are rarely much larger than 

 the masseters, and often very much smaller. When 

 we look at Thylacoleo, ^we find not only the enormous 

 temporals and only moderate masseters, but everything 

 else about the skull seems to be built on carnivorous 

 lines. Owen has shown the wonderful similarity which 

 exists between the molar machinery in Thylacoleo and 

 the lion, and it is hard to conceive as possible any other 

 cause giving rise to such a specialisation in Thylacoleo 

 than that which led to a similar specialisation in the cat 

 tribe. Another most striking feature is to be seen in 

 the condition of the incisors. Leaving out of considera- 

 tion the mode of implantation and structure of the teeth 

 both confirmatory of the carnivorous hypothesis 

 there is one point which appears to me absolutely con- 



