352 DARWINISM TO-DAY. 



pending on whether in making the matings pure dominants 

 or cross-bred dominants happen to be used). Thus the 

 sudden appearance in the second generation of the latent or 

 recessive characteristic, and its breeding true, are occur- 

 rences which might readily be interpreted as the appearance 

 of a mutation or true-breeding sport by an observer unac- 

 quainted with the ancestry of the' individuals under his eye. 



Alternative Theories to Explain Secondary Sexual Char- 

 acters. Before closing this discussion of theories which 

 have been proposed as substitutes for the Darwinian selec- 

 tion theories to explain the actual conditions in the organic 

 world as we see it to-day, and as we know it to have been 

 in past ages, we should mention, at least, the few attempts 

 to formulate a substitute explanation for the existence of 

 secondary sexual characters. The discrediting of the sexual 

 selection theory as such an explanation is certainly nearly 

 complete. But it is interesting to note how lame and uncon- 

 vincing are the proposed substitute explanations. 



The first, and most appealing one, is the explanation that 



the extra plumes, wattles, horns, the unusual display of 



bright colours, etc., of the males are simply the 



Extra growths manifestations of an extra growth-force or 



extra vigour, vigour exhibited by the male in the breeding 



season. The female also may be endowed with 



extra growth-vigour at this time, but it goes, in her case, to 



the formation of ova, to the storing up of food in or around 



the egg cells. The songs, the dances, the violent play and 



antics of the males common to many species of birds, insects, 



spiders, etc., are also attributed to this special or sexual 



vigour. 



Now while such secondary sexual characters as colour, 

 plumes, wattles, etc., might perhaps well enough seem to 

 be the outcome of an extra growth-vigour, what about such 

 special male characters as the stridulating organs of male 

 katydids and crickets, and other similar complex, highly 



