EGGS AND LABVM OF A SEA-BULLHEAD. 293 



to see whether she laid any more eggs.* Beyond this she 

 showed no interest in the eggs, nor did she pay any attention 

 when they were interfered with. It may be pointed out that no 

 other Bullhead had been in the aquarium, and that no fresh 

 sea-water had been introduced into the tank for some weeks. It 

 would therefore seem that this female had been fertilized in the 

 sea, from which it had been taken six days before the eggs 

 were laid. 



On the afternoon of February 17th (that is, on the twenty- 

 first day after laying) the eggs were transferred to another tank, 

 in order to guard against the danger of the coming larvse being 

 eaten by the several individuals of the Goby (Gobius paganellus) 

 and the two individuals of the Prawn (Palcemon serratus) which 

 lived in the same aquarium, though neither Gobies nor Prawns 

 had touched the eggs. Two hours later the larval Bullheads 

 began to break away from the egg-mass, and hatching went on 

 at intervals during that day and the next. Hatching was 

 possibly hastened by this removal, for according to Ehrenbaum 

 the eggs are laid in March and April and hatched six to seven 

 weeks later. f Less than a quarter of those which had arrived 

 at a stage when they were able to escape actually hatched from 

 the egg, so that out of nearly two thousand eggs only about a 

 hundred larvae were obtained. For several days before hatching, 

 the larvse could be seen making occasional sudden movements 

 within their egg-envelopes, and their eyes, which were of a 

 bright metallic blue or green colour by reflected daylight, or a 

 bright copper colour by the light of the electric lamp above the 

 aquarium, were very conspicuous. Each transparent larva, 

 which was 4*5 mm. in length at hatching,"]; had a protuberant 

 abdomen, long tail, and two large membranous semicircular 

 pectoral fins.§ The larva could easily be detected in the water 



* M'lntosh, " Remarks on the Eggs of British Marine Fishes," ' Nature,' 

 vol. 34, p. 148, says that, so far as was known, deposition of the eggs is 

 performed rapidly in the Cotti. f Op. cit. p. 137. 



I The length of the larva at hatching is given by different authorities as 

 follows: — Cunningham (op. cit. p. 72), 5*7 mm.; Holt (op. cit. p. 27), 

 5*71 mm. ; Fabre-Dornergue & Bietrix (op. cit. p. 168), 4 - 5 to 5*5 mm. 

 Ehrenbaum (op. cit. p. 138), 5 - 5 to 5 - 8 mm. 



§ Figures of the newly-hatched larva are given by Cunningham (op. cit. 

 plate iv.), Holt (op. cit. plate v.), and Ehrenbaum (op. cit. plate hi.). 



