^7" Patten : Dimorphis^n in Eggs, etc. 



These I will refer to in a moment. The clutch in question, of 

 which I give a photograph, consisted of four eggs. They were 

 found on May 30th, 1908, in a perfectly normally-built Thrush's 

 nest, well hned with a wall of dung, bits of rotten wood, and 

 caked moss. The nest was built in a laurel-bush, and, when 

 first discovered, the bird was sitting, and her identity thus 

 secured. The off chance of the unspotted egg being that of a 

 Starhng is rendered all the more remote by the fact that Star- 

 lings were not breeding in the immediate neighbourhood, nor 

 indeed can I find an instance of a Starhng laying in a Thrush's 

 nest. That Thrushes have laid in Blackbirds' nests is a known 

 fact, and there is no reason to doubt that occasionally a Black- 

 bird may take possession of a Thrush's nest. Moreover, the 

 Blackbird has been known to lay blue unspotted eggs. In the 

 present instance, I do not think for a moment that the egg was 

 introduced by another bird into the nest, yet, from the observa- 

 tions made upon it prior to its being blown, suggestions seem to 

 arise regarding the possibility of its being other than a member 

 of the clutch. In measurement it is slightly longer than any 

 of the spotted eggs, but the difference is so trivial as to call 

 for no significance. Indeed, as may be seen from the measure- 

 ments given below, all the eggs of the clutch exceed the average 

 measurement in length. Its broadest measurement corres- 

 ponds with two others of the clutch, while the remaining one 

 is only i mm. narrower than these. In breadth all the eggs 

 of the clutch may be said to attain to the average measurement 

 laid down. But in the colour and texture of the shell, the un- 

 spotted egg, examined unblown, showed two marked- peculiar- 

 ities. The gloss, which was present in the spotted shells, was 

 absent, and the texture of the shell was rougher and more porous. 

 The other feature attracted my attention still more, namely 

 the difference in the ground-colour. This was much more 

 apparent when the specimen was viewed in strong sunlight. 

 The shell of the unspotted egg appeared lighter in shade, and 

 of a truer blue colour than the shells of the three spotted eggs. 

 But the latter, which shewed a slight greenish tinge, became, 

 when blown, almost identical in shade with the unspotted shell. 

 The reason soon became obvious, for, on blowing out the con- 

 tents, I was surprised to find that the unspotted shell contained 

 only a remarkably small and very pale yellowish-white yelk, 

 which, amidst the mass of glary albumen was very inconspicuous. 

 Hence the strong hght, more or less transmissible through the 

 shell, did not mingle to any extent with a rich and large yellow 

 yelk-ball, and thereby produce a greenish effect. 



