292 THE ZOOLOGIST. 



NOTES ON THE EGGS AND LAHV/E OF A SEA- 

 BULLHEAD (COTTUS BUB A LIS). 



By H. N. Milligan, F.Z.S. 



A healthy female Cottus bubalis of about six inches in 

 length, from Weymouth, was placed on January 23rd, 1915, 

 in an aquarium at the Horniman Museum, where it lived until 

 May 9th. 



The Bullhead usually lay upon, or partly buried in, the 

 shingle at the bottom of the aquarium, but at about 9.30 on the 

 morning of January 28th I noticed that the fish was clinging by 

 means of its spreading pectoral fins to the vertical rockwork at 

 the back of the tank, and it remained there for several hours, 

 certainly until 5 p.m. and possibly longer. Some time before 

 9.30 on the following day the fish moved away, and in a shallow 

 depression amongst the rocks over which it had lain was a 

 flattish mass of pale orange-coloured eggs. The mass, which 

 was roughly oval in shape, was about two inches in length and 

 one and a half inches in breadth. It was ascertained later that 

 the number of eggs in the mass was nearly two thousand, and 

 at its deepest part the mass was about twelve layers of eggs in 

 thickness. The average size of the eggs was 1*5 mm.* The 

 eggs adhered together at laying, but they became harder and 

 more firmly attached as the days passed. Not more than a 

 quarter of the eggs in the mass developed. 



The day after laying, the Bullhead returned to the egg-mass, 

 and remained on it for about two hours, but it was impossible 



* J. T. Cunningham, " On Some Larval Stages of Fishes," ' Journal 

 Marine Biological Association,' N. S. 2, 1891-2, p. 72, gives the diameter of 

 the eggs examined by him as 1'7 mm. E. W. L. Holt, " On the Eggs and 

 Larval and Post-larval Stages of Teleosteans," ' Scientific Transactions of 

 the Eoyal Dublin Society,' vol. 5, ser. 2, 1893, p. 27, observes that he found 

 the eggs larger in some clutches than in others, the largest being 1*88 mm. 

 Fabre-Domergue & E. Bietrix, "Becherches Biologiques applicables a la 

 Pisciculture Maritime," ' Annales des Sci. Nat.,' vol. 4, 1897, give the 

 diameter of the egg as 1*5 to 1*6 mm. E. Ehrenbaum, " Eier und Larven 

 von Fischen der Deutschen Bucht. 3. Fische mit festsitzenden Eiern," 

 ' Wissenschaftl. Meeresuntersuch. in Kiel,' N. F., Band 11, 1910, p. 137, 



