THE EEL FAMILY. 453 



conger lays its eggs on or in the sea-bottom and not pelagically, 

 for in fish with pelagic eggs fertilization is ensured by vast 

 ma,sses of eggs and spermatozoa being set free in close proximity 

 in the mid-water at the same time. Great numbers of each sex 

 usually congregate together so that the limits of time and space 

 being very confined, the probability of eggs avoiding fertilization 

 is made as small as possible. Such limitations are obviously 

 impossible in fishes which mature at various seasons of the year, 

 for, even if congregations took place, only a small proportion of 

 each sex would be ripe at a given time. These considera- 

 tions are exaggerated by the extremely rapid and simultaneous 

 ripening of the whole contents of the ovary. Other indirect 

 evidence in favour of demersal spawning is found in the presence 

 of certain secondary sexual characters. It has been pointed out 

 above (see Dragonet) that the fishes with demersal eggs are 

 those, as a rule, which show secondary sexual characters coupled 

 with a tendency to ' pair.' We have seen that the common eel 

 shows distinct secondary sexual features which are emphasised 

 at the breeding season and the conger in this seems to resemble 

 its ally. Mr Cunningham finds that — 'in the female (conger) 

 the outline of the head when looked at from above is triangular, 

 the snout being pointed ; in the male the same outline is much 

 less pointed, the snout being distinctly blunter. Also in the 

 female the dorsal surface of the snout in front of the eyes is 

 arched, so that a transverse section of the dorsal surface is the 

 arc of a circle ; in the male the surfaces of the snout are flat, 

 its sides above the mouth being perpendicular and the upper 

 surface almost level, so that a transverse section forms three 

 sides of a square.' The males also appear to be much darker 

 on the ventral surface and usually to have more prominent eyes. 



Thus the presence of secondary characters and the indefinite 

 spawning-period point to either a demersal spawning-habit, or 

 as in the case of the dragonet to a pairing instinct combined with 

 a pelagic egg. This latter seems the more likely alternative 

 when we take into consideration the enormous fecundity of the 

 conger, a feature which is characteristic of fishes with a pelagic- 

 spawning habit. 



As regards the numerical relation of the sexes. Brock has 



