FISHES 



195 



elongation of the rays never exceed 5*2 inches in length, but 

 that no specimens of either sex with the elongated rays have 

 ever been found which are under that limit of length. If 

 A. lophotes were a distinct species therefore, it would be a 

 species of which no young specimens existed, an obvious 

 reductio ad dbsurdum. 



Mr. E. W. L. Holt 1 has recently found that sexual 

 maturity occurs in specimens which are still in the undiffer- 

 entiated condition, that is to say, specimens in which the 

 anterior dorsal rays were not elongated were found to be 

 sexually mature, both males and females. In June, in Teign- 

 mouth Bay and Tor Bay, Mr. Holt obtained ripe ova and milt 

 from five females 5 J to 6 J inches long, and three males 5 to 5 J 

 inches long. The ova were artificially fertilised, and went 

 through the process of segmentation. They died, however, 

 before the embryo was formed, which may possibly be an in- 

 dication that the ova and milt were not perfectly mature. 

 Later, in July, the same naturalist obtained ova and milt from 

 " differentiated " specimens over 6 inches long. The eggs are 

 pelagic, and have an oil globule, and the few that were 

 measured showed that the eggs of the smaller females were 

 smaller than those of the larger. It is known, however, that 

 smaller female fish of a species may have slightly smaller 

 eggs than the larger, and the measurements were not 

 numerous enough to show that the difference in the size of 

 the oil globule was constant. That the males should be 

 mature, or should at least produce milt before the secondary 

 peculiarities are fully developed, is by no means an excep- 

 tional occurrence ; in fact, it has been observed in many 

 other cases, among birds, for example, and it is also true in 

 many mammals. It is a general truth that unisexual male 

 characters do not attain their full development till after 

 puberty, and that they only begin to develop at puberty. 



1 Jour. Mar. Biol. Assoc, vol. v. No. 1. 



