SEXUAL SELECTION. 223 



er to its own male and female sex to the hybrid offspring of either 

 sex. The same fact is likewise manifest, when characters proper 

 to the male are occasionally developed in the female when she 

 grows old or becomes diseased, as, for instance, when the com- 

 mon hen assumes the flowing tail-feathers, hackles, comb, spurs, 

 voice, and even pugnacity of the cock. Conversely, the same thing 

 is evident, more or less plainly, with castrated males. Again, 

 independently of old age or disease, characters are occasionally 

 transferred from the male to the female, as when, in certain breeds 

 of the fowls, spurs regularly appear in the young and healthy fe- 

 males. But in truth they are simply developed in the female; for 

 in every breed each detail in the structure of the spur is trans- 

 mitted through the female to her male offspring. Many cases will 

 hereafter be given, where the female exhibits, more or less per- 

 fectly, characters proper to the male, in whom they must have 

 been first developed, and then transferred to the female. The 

 converse case of the first development of characters in the female 

 j,nd of transference to the male, is less frequent; it will therefore 

 be well to give one striking instance. With bees the pollen-col- 

 lecting apparatus is used by the female alone for gathering pollen 

 for the larvae, yet in most of the species it is partially developed in 

 the males to whom it is quite useless, and it is perfectly developed 

 in the males of Bombus or the humble-bee.'"' As not a single other 

 Hymenopterous insect, not even the wasp, which is closely allied 

 to the bee, is provided with a pollen-collecting apparatus, we have 

 no grounds for supposing that male bees primordially collected 

 pollen as well as the females; although we have some reason to 

 suspect that male mammals primordially suckled their young as 

 well as the females. Lastly, in all cases of reversion, characters 

 are transmitted through two, three, or many more generations, and 

 are then developed under certain unknown favorable conditions. 

 This important distinction between transmission and development 

 will be best kept in mind by the aid of the hypothesis of pangen- 

 esis. According to this hypothesis, every unit or cell of the body 

 throws off gemmules or undeveloped atoms, which are transmitted 

 to the offspring of both sexes, and are multiplied by self-division. 

 They may remain undeveloped during the early years of life or 

 during successive generations; and their development into units 

 or cells, like those from which they were derived, depends on ttieir 

 aflSnity for, and union with other units or cells previously devel- 

 oped in the due order of growth. 



Inheritance at corresponding Periods of Life. — This tendency is 

 well established. A new character, appearing in a young animal. 



''' M. Muller, 'Anwendung: der Darwin'schen Lehre,' &c. Verh. 

 Jaiirg, xxix. p. 42. 



