ii6 DIVERSIONS OF A NATURALIST 



ence of " complemental males," as Darwin called them, 

 existing apparently in order to fertilize the eggs should 

 they escape fertilization by the ordinary monoecious 

 individuals, was a new thing. And it was doubted and 

 disputed when Darwin described his observations fifty- 

 six years ago. They were, in fact, by many regarded 

 as a distinct species parasitic upon the larger barnacles 

 on which they were found until Darwin's conclusion as 

 to their nature was confirmed by the report of Dr. Hoek, 

 on the barnacles brought home by the " Challenger " 

 expedition. 



It is an interesting fact that recent studies have 

 shown that in some of the barnacles with dwarf males 

 (species of Scalpellum) the large individuals are no 

 longer monoecious, but have become purely females, 

 whilst in some other species dwarf males have been 

 discovered which have rudimentary ovaries. Thus we 

 get gradations leading from one extreme case to the 

 other. Darwin always felt confidence in his original 

 observations on this matter, and was proportionately 

 delighted when, after thirty years, his early work was 

 proved to be sound. In the Natural History Museum 

 at the Darwin centenary in 1 909, a temporary exhibition 

 of specimens, note-books, and letters associated with 

 Darwin's work, was brought together. His original speci- 

 mens and drawings of Cirripedes and of the wonderful 

 little " complemental males " of the barnacles were placed 

 on view. 



