18 INIKODUCTION. 



Dugong). This creature has enormous tusks which continue to 

 grow as the animal grows, and are even larger in proportion m 

 the adult than in the young. Thus the tusks of the female 

 grow more quickly than the skull. They are nevertheless wholly 

 functionless in the female ; that is to say, they are used neither 

 as tusks nor as teeth, for they are completely encased in the 

 upper jaw-bone, and the blunt point is covered by a huge fleshy 

 upper lip forming a snout. The male Dugong uses his tusks, 

 which project at the sides of the mouth, as weapons or for other 

 purposes, as is proved by the fact that the outer surface of 

 the points of the tvisks is, without exception, much worn in 

 every male skull found in our collections. The tusks of the 

 female Dugong are rudimentary and functionless as teeth ; 

 however, like all similar rudimentary organs, they ai-e not 

 included in the above-mentioned class of functionless organs, 

 which, in spite of their immense variety and often conspicuous 

 size, cannot be regarded either as true organs now exercising 

 their functions, or even as true organs in a degraded condition, 

 such as are known in scientific parlance as ' morphological cha- 

 racters,' in contradistinction to ' physiological characters,' that is 

 to say, those whose use is obvious or well-known. The exist- 

 ence of such morphological characters has been affirmed, as I 

 have said, even of animals ; but it still seems doubtful whether 

 those organs and parts of the animal body which we include in 

 this category do in fact belong to it, and are not perhaps thus 

 classed merely because as y3t we know nothing of their func- 

 tional importance. Even when we assign to such parts the 

 smallest possible importance in the life of the animal, we ought 

 not to forget that they consist of living cells, or are directly 

 dependent on them. Hence we are justified in propounding the 

 thesis that every part which we are accustomed, from its lack 

 of conspicuous physiological character, to regard as a morpho- 

 logical character, must nevertheless have a certain functional 

 value in the general economy of the animal, since it must pro- 

 duce a fraction, however small, of the material which is formed 

 in the living body, and must possess a proportionate share of all 

 its properties. 



At the same time it cannot be disputed that even in 



