204 



SKXIWL DIMORPHISM 



position, and the two ascended towards the surface of the water. 

 In this movement the male used chiefly his pectorals, aided by 

 the caudal and the hinder parts of the second dorsal and the 

 ventral. The first dorsal of the male was now depressed, and 

 lay extended along the back. The female moved her pec- 

 torals slightly, and occasionally her caudal, but the male 

 appeared actually to carry the female up through the water. 



As the pair ascended, their ventral surfaces were slightly 

 inclined to each other, so that the edges of their anal fins 

 were in contact for some distance. The elongated genital 

 papilla of the male was turned towards the female, and 

 the ova were probably discharged through the space be- 

 tween the ventral fins, and fertilised by the milt which was 

 emitted in the same direction. The discharge of the ova 

 and milt could not be actually seen, the ova are very small 

 and transparent, and milt would not necessarily be seen in 

 small quantities. It is certain that ova were emitted and 

 fertilised in the tank during the period when the observa- 

 tions were made, as they were obtained by placing a fine net 

 at the overflow of the tank, and were hatched in separate 

 jars. 



The ascent of the pair of fish was very slow. When they 

 reached the surface the male and female sometimes separated 

 at once, but more often continued together for a time, with 

 their snouts bobbing out of the water. Sooner or later the 

 two separated, and then darted rapidly to the bottom. Occa- 

 sionally the male or the female ascended to the surface alone, 

 but not often. The female in pairing sometimes took the 

 right, sometimes the left side of the male. 



During the first period reproductive activity lasted only 

 eight days, and only one female was engaged. Pairing took 

 place between 9 A.M. and noon, after which the males ceased 

 to sport, and usually buried themselves in the gravel. At 

 about 4 p.m. activity recommenced, but in a much less degree, 



