26 



HISTORY OF CRUSTACEA. 



CHAP. IV. 



long series of structures running into one another, but 

 only two forms united by no intermediate terms (figs. 8 

 and 9). The males would be unhesitatingly regarded 



Figs. 8 and 9. 3 



as belonging to two well-marked species if they did not 

 live on the same spot, with undistinguishable females. 

 That the two forms of the chelae of the males occur 

 in this species is so far worthy of notice, because the 

 formation of the chelae, which differs widely from the 

 ordinary structure in the other species, indicates that 

 it has quite recently undergone considerable changes, 

 and therefore such a phenomenon was to be expected 

 in it rather than in other species. 



3 Figs. 8 and 9. The two forms of the chelae of the male of Orchestia 

 Darwinii, magn. 45 times. 



