ZOOLOGY 



Primary 



sexual 



characters 



Secondary 



sexual 



characters 



On the other hand, there are groups of animals, such as 

 the common snail, in which both male and female 

 organs exist in the same individual. Snails are there- 

 fore said to be hermaphrodites (from Hermes and Aphro- 

 dite), but they are not self-fertile ; they pair as do other 

 sexual animals. 



2. Sexual characters are those which distinguish sex. 

 On analysis, we find that they are of two different sorts. 

 The primary sexual characters are those which have to 

 do with the sexual function itself, which is essentially 

 the production of gametes. It is on account of this con- 

 ception of sex that botanists object to speaking of male 

 and female plants or flowers ; they point out that these 

 organisms give rise to the gametophytes or true sexes, 

 which produce the gametes. If we object to this on the 

 ground that the so-called gametophyte generation is so 

 insignificant, they point out that in the higher flowerless 

 plants it is conspicuous, being known as the prothalhum. 

 Ferns produce spores, which give rise to these prothallia, 

 and these in turn produce the gametes. 



Secondary sexual characters are those which accom- 

 pany sex, and are nearly always of some importance in 

 relation to it. Such, for instance, are the bright plumes 

 of certain male birds, or peculiarities of the voice. Al- 

 though these two groups of characters appear so distinct, 

 they do in fact grade into one another, unless we restrict 

 the first entirely to the gamete-producing function. 

 Structures existing for the preservation and nutrition of 

 the zygote or fertilized cell can hardly be excluded from 

 the group of primary sexual characters, since without 

 them, in the animals in which they occur, reproduction 

 would be impossible. From these there is actually 

 every gradation, to characters which appear to have no 

 functional relation to sex. Nevertheless, in a broad 



