The Evidence from Sexual Characters. 185 



sion of a very peculiar clasping organ, figure 23, upon 

 the first swimming appendage of the abdomen. The 

 corresponding appendage, figure 24, of the adult fe- 

 male is like the other abdominal appendages of both 

 sexes, and we must believe that the peculiar form, in the 

 male, is due to recent modification. It is therefore in- 

 teresting to note that, before the male reaches maturity, 

 the limb in question is exactly like the other abdominal 

 appendages of the adult male or adult female. The 

 male Lucifer differs from the female in the shape of the 

 last segment of the abdomen, and the outline of the 



FIG. 23. First abdominal append- FIG. 24. The corresponding append- 

 age of a male Lucifer. age of the female. 



exopedite of the tail-fin is peculiar. These differences 

 are very slight, as will be seen by comparing the termi- 

 nal segments of the male, figure 25, with those of the 

 female, figure 26, and it is hardly possible that they 

 are of any direct service in reproduction. The fact 

 that, in the young of both sexes, these parts are like 

 those of the adult female, and that their peculiarities in 

 the adult male are due to a final change which does not 

 occur in the female, indicates that race- modification has 

 gone a little further in the male Lucifer than it has in 

 the female. 



