MAINE AGRICULTURAL EXPERIMENT STATION. I9I3. 279 



attractive to the female. It is supposed on this theory that 

 those males which had the largest comb and wattles would be 

 most attractive to the females and would, therefore, stand a 

 better chance of mating and perpetuating themselves in the 

 ofifspring. Like many other secondary sexual characters the 

 comb and wattles while present in both sexes are very much 

 better developed in one sex than in the other. It is doubtful 

 whether the sexual selection theory really accounts for the 

 presence of large comb and wattles in the male. It is more in 

 line with modern biological opinion to suppose that these or- 

 gans are merely one representative of the surplus of growth 

 energy and physiological vigor which characterizes the male as 

 compared with the female. It is doubtful, in other words, 

 whether they have any selective value. 



It is quite certain that neither the combs nor wattles serve 

 any useful physiological function. That is to say, a bird from 

 which these structures has been removed is quite as healthy 

 and lives as long and is fully as able to perform all its vital 

 functions as a bird which possesses them. They are in some 

 degree, however, and in a manner which is not yet fully under- 

 stood, connected or correlated with the primary sexual organs 

 (that is, the testes in the male and ovary in the female). Fur- 

 ther proof of this has recently been furnished by the work of 

 an English biologist who shows that throughout the life of a 

 hen every period of laying is preceded by an enlargement of 

 the comb. This enlargement is due to an actual growth of 

 tissue in the comb substance. The enlargement in many cases 

 is not marked and can only be detected by very accurate 

 measurements. 



The fact that the comb and wattles diminish in size and 

 become pale in color during periods of physiological depression 

 such as molt or in various diseases finds its physiological ex- 

 planation in the considerations which have been advanced above. 

 These organs being in the nature of non-essential excrescences 

 or ornaments, with a very considerable blood supply when the 

 bird is in health and vigor, it stands to reason that when that 

 vigor is diminished for one reason or another, the supply of 

 blood and nutriment to the tissues of these organs will be 

 diminished in order that it may be diverted to other more vital 

 parts. The reduction of the comb in size and color during 



