io E VOL UTION AND DISEASE. 



indeed we are fully justified in stating that this nasal 

 horn of the rhinoceros is a gigantic wart (fig. 5). Pro- 

 fessor Flower recently exhibited at the Zoological 

 Society the skin from the head of a rhinoceros shot 

 in Central Africa with three nasal horns. The accessory 

 one measured twelve centimetres in height and more than 

 forty-two in circumference. It 

 was situated in the same line 

 posteriorly to the normal horns. 

 It was structurally a wart. That 

 cutaneous horns should arise in 

 oxen and other hollow-horned 

 ^ruminants (Cairicornid) need not 

 surprise us when we reflect that 

 [the corneous caps of their natural 

 horns are modified portions of 

 the integument. 



Birds not^ in frequently exhibit 

 wart-horns of this character, and 

 an example growing from the leg 

 of an oyster-catcher is shown in 

 fig. 6. Such horns, whenever 



FIG. 6. The leg of an Oyster s 



Catcher (Hcematopvs ostra- they have been observed in birds, 



legns] with a large wart-horn. fonow ^ usual ^^ of 



dermal organs in general, and are shed with each 

 moult and reproduced with the new feathers. The 

 horn on the leg of the oyster-catcher when compared 

 with the size of the bird is very large. It is represented 

 one-fourth its natural size. 



The shedding of pathological cutaneous horns and 

 their subsequent reproduction has more than one 



