196 SEXUAL DIMORPHISM 



A more remarkable suggestion made by Mr. Holt in 

 reference to this subject is the following: A. laterna may 

 confidently be considered to exist in the Mediterranean, being 

 in all probability identical with the A. conspersus of the 

 Mediterranean ichthyologists. It is certain that a specimen 

 of the lophotes form was sent to Dr. Giinther from Palermo. 

 Specimens of the laterna form have been taken on the south- 

 west coast of Norway, but none of the lophotes form have 

 been mentioned from that region. Mr. Holt suggests, there- 

 fore, that the differentiated or lophotes form is never developed 

 on the coast of Norway, but that the fish remains perma- 

 nently, and reproduces, in the laterna form. This conclusion 

 rests only on negative evidence, and is, in my own opinion, 

 improbable. The lophotes form appeared for many years to 

 be a rarity in British waters, and, considering how little the 

 trawl is used in Norwegian waters, it would seem more 

 probable that specimens in this condition could be captured 

 off the Norwegian coast if sufficient endeavours were made to 

 obtain them. It will probably be found, if an opportunity 

 ever occurs of observing the habits of the fish when 

 spawning, that the elongation of the anterior dorsal fin-rays 

 is associated with habitual erection or vibration of these rays 

 during sexual excitement, as in the Dragonet. 



An elongation of certain fin-rays occurs as a unisexual 

 male character also in Pseudorhombus ocellatus, as described 

 by Dr. Giinther in his Report on the Shore Fishes of the Chal- 

 lenger Expedition (vol. i., 1880). The description is as follows : 

 " The dorsal fin commences above the nostrils, is not scaly, 

 and terminates close to the caudal, its anterior rays being 

 shorter than the middle ones. In the male the thirteenth to 

 nineteenth rays of the dorsal and the seven anterior of the 

 anal are prolonged into long filaments." The specimens were 

 obtained outside Nares Harbour, in the Admiralty Islands, at 

 a depth of 152 fathoms. It is curious in this case that, 



