14 



A. E. HEFFOliD. 



Such, for example, were the conditions under whicli Holt (lib, 

 p. 31) was enabled to identify the eggs of T. cucvhis taken in April 

 and May off the west coast of Ireland, and similarly Ehrenbaum 

 (5c, p. 248) has made extensive measurements of planktonic and 

 artificially fertilized ova of T. r/urnardus in the ISTorth Sea, the main 

 piirpose in the latter case being to distinguish between grey gurnard 

 eggs and those of the mackerel, which may to a certain extent coincide 

 in diameter and size of oil-globule. 



The following table shows the dimensions of artificially fertilized 

 Trigla ova from four species which have previously been described 

 by various observers : — 



Besides the above four species, Trigla lyra, L., commonly known as 

 the Piper, occurs off Plymouth in appreciable quantities, but its ova 

 have never been described. A further difficulty is introduced by the 

 great variation which is shown by the eggs of the same species 

 observed in different regions and at different times. In spite of this, 

 however, Canu (3b, p. 72) has stated that, as regards the eastern part 

 of the Channel, the eggs of T. hirundo exceed in diameter those of all 

 other members of the genus, but he does not give any actual observa- 

 tions to support this statement. 



Out of my own collection, during the summer of 1909, I can only 

 refer three eggs with absolute certainty to the Trigla genus. As to their 

 specific identity I can say nothing, except that T. lincata appeared to 

 be the most common species oft' Plymouth at the time (July) and may 

 possibly have been the parent fish. There are few descriptions of 

 gurnard eggs and larvae on record at present, so it may serve a useful 

 purpose for future comparison if I briefly give here my own observa- 

 tions. On the 5th of July an egg was taken about 2| miles north-w^est 

 of the Eddystone. Its diameter was 1*4 mm., and it contained an oil- 

 globule of 022 mm. Observed on the same day, the blastodisc had 

 almost half enveloped the yolk. Next day the embryo had formed ; 



