2 78 STUDIES IN THE EVOLUTION OF ANIMALS 



jaw, if both jaws were originally long. Then such a monstrous 

 weapon having been found useful, it would increase to a certain 

 advantageous maximum, by constant use and direction of nervous 

 energy thereto. There is nothing in such a monstrosity, supposing 

 the abnormal size to have originated in one, to lead us to suppose 

 that these two fishes would have been debarred from procreating 

 with their normal fellows, and perpetuating this abnormality. 



Then the Hammer-headed Shark {Zygcend) leads to the thought 

 that such an aberration may have originated monstrously by a 

 certain projection of both ocular regions. 



Again, the extinct Dinotherium giganieuni may have had its 

 turned-down lower jaw tusks originating in a sudden abnormal 

 form ; and the immense upper jaw tusks of Elephas Ganesa (loj 

 feet long, and massive in proportion) may have become so large 

 by an abnormal growth. Indeed it may have been those enormous 

 tusks which helped to cause the extinction of that particular form 

 owing to their great unwieldiness, and consequent disadvantage in 

 the struggle for life. In other words, they may have increased 

 beyond the maximum of usefulness. i 



1 In the Temple Flower Show of 1894 there was a Sedum ticketed Sedum virens 

 monstrosum, consisting of a fasciation of stems covered all over with small fleshy 

 leaves, and resembling a cockscomb (probably Sedum reflexum cristatim of Dr. 

 Masters). Its parent form is said to have trailing stems. Then there was Scolopen- 

 drium vulgare scalariforme, said to be a monstrous form of the common Hartstongue fern. 

 There cannot be much doubt that sudden monstrosities of similar and other natures may 

 have originated new genera. 



One often sees a fusion of twin flowers producing a larger many-petalled and many- 

 stamened flower. There was one such in Lilium monadelphum Szovitsianum. 



Mr. Heal informed me that he had a monstrous Streptocarpus consisting of a fusion 

 o(four flowers. He tried to perpetuate it, but its descendants reverted to the one-flower 

 type with five petals of the Gloxinia shape. 



No doubt this obliteration of a monstrous type, and reversion to ancestral forms, 

 would often occur in nature, but among millions of such phenomena there might be 

 some which cotild be perpetuated, and we know that six-digitate individuals can be 

 perpetuated in spite of dilution with normal blood. 



