i io EXPERIMENTAL EVOLUTION LECT. 



flowers. 1 This condition may vary from one year to 

 another, in the course of the lifetime of the plant. It 

 even seems that in normally male plants, this condition 

 may put in an appearance. Ch. Martins 2 observed at 

 Moritpellier a male Chamcerops humilis which yielded 

 only male flowers from 1851 to 1861 ; in 1861 this 

 plant produced some female flowers, quite normal, 

 since the seed from these flowers yielded vigorous 

 young plants; and in 1862 a large proportion of 

 female flowers were to be seen. This last fact is of 

 real importance, as showing that sexual variability 

 may exist to a high degree. 



Another very interesting form of variability is that 

 which may be observed in individual evolution or 

 development. Although there are numerous cases of 

 this sort, and although a large number of instances 

 might be quoted where the individual evolution is 

 readily arrested or modified through different circum- 

 stances, none seem more carefully ascertained than 

 those which Camerano has published. This writer has 

 investigated what Kollmann has called Neotenia in 

 Amphibians. Neotenia is the lengthening (for an 

 indefinite time) of the period during which Amphibians 

 are gill-breathers. Every one knows that, at first, 



1 Carriere, Sur FAilanthus glandulosa a propos des Sexes. Rev. 

 Horticole. 1872, p. 234. 



Ch. Martins, Transformation d?un Chamcerops humilis male en 

 polygame. Rev. Horticole, 1862, p. 353. 



