VOL. viii] BLAKENEY POINT TERNERY. 261 



of eggs, but chiefly to try and correlate mottling, ground- 

 colour and size. The results of last year's work have 

 not been got out yet, though they should prove more 

 valuable than those of the previous season. It would 

 be waste of time and space to repeat here what has 

 already been pubhshed with regard to 1913 results.* 



Still, one or two conclusions are worthy of repetition. 

 Quoting from Biometrika (Rowan, Parker and Bell) : "A 

 point seemed worth consideration : assuming the pig- 

 ments to be deposited on the egg in its passage through 

 the oviduct, it was conceivable that greater pressure 

 might indicate greater intensity of pigmentation. We 

 accordingly selected the broader egg in each clutch 

 and investigated from every pair of eggs in the same 

 clutch whether the broader or narrower egg had the 

 larger mass of mottling and greater density of groimd- 

 colour. We reached the following results : — 



" The broader egg in every possible clutch pair has — 



Greater mottling in 26 cases. More dense grovmd- colour in 25 cases. 



The same „ 37 



Less „ 40 



The same ,, „ ,, 39 



Less dense „ ,, „ 37 



Perhaps not very much stress is to be laid on these 

 results, but they suggest that the total amount of 

 pigment deposited is less the broader the egg, i.e. for 

 the same bird a relatively smaller egg vnW be more 

 pigmented. A solution of this rather unexpected result 

 may, perhaps, be found in the suggestion that the total 

 amount of pigment is the same in both eggs, but the 

 mottling and ground-colour will appear denser on the 

 smaller egg. The point deserves consideration on the 

 basis of larger numbers and possibly better defined 

 measures of pigmentation." 



Variation in the ground-colour and mottling is infinite. 

 It has often been maintained by some authorities that 



* See Biometrika, Vol. X., No. 1, pp. 144-168, "On Homotyposis 

 and allied characters in the eggs of the Common Tern." Also 

 " Some observations on a Tern Colony," Knowledge, Vol. XXXVII., 

 No. 547, pp. 52-54, reprinted in the Journal of Ecology, Vol. II., No. 1, 

 pp. 18-20. 



