FISHES 191 



of constitutional conditions associated with maturity in the 

 male sex. We might suppose that the spines have no special 

 function and confer no advantage, but that the degeneration 

 of the scales has proceeded further in the female than in the 

 male, just as it seems that the loss of hair on the body is 

 more complete in the female than in the male of the human 

 species. On this view it is difficult to understand why the 

 spines are absent in the young males, and only appear at 

 sexual maturity. This, again, is paralleled by the history of 

 the beard and moustache in man. 



At present we do not know that the spinulation of the 

 scales in the male plaice performs any function in the rela- 

 tions of the sexes or in the life of the male, and therefore it 

 is impossible to suggest any kind of irritation or stimulation 

 which might be regarded as the cause of the character. 

 Observations have been made on the spawning of soles in 

 the aquarium of the Laboratory of the Marine Biological 

 Association at Plymouth, but they did not support the sup- 

 position that there is any definite apposition of the bodies of 

 male and female in the process of spawning. Mr. Butler, who 

 watched the spawning soles, states l that the eggs appeared 

 to be shed one at a time, each after a particular movement, 

 the fish raising its head and bringing it down again with 

 force on the sand. It seemed that this movement wafted the 

 egg towards the tail, because a single egg commonly appeared 

 above the tail of a fish after its performance. The actual 

 exit of either ovum or milt was never observed. The soles 

 lay about on the sand indiscriminately. One of them would 

 from time to time move leisurely to another place, and in 

 passing by or over a companion would take notice of it by 

 feeling it with the lower side of its head, where the tactile 

 filaments are situated, but this never led to anything of the 

 nature of pairing, the fish would again move on and continue 



1 Journal Mar. Biol. Assoc, vol. iv. No. 1, p. 5. 



