302 Patten : Dimorphism in the Eggs of the Hoiise-Sparroiv. 



embryos were living when the eggs were at first removed. 

 But quite a different state of affairs presented itself in the case 

 of the two curiously marked eggs (Plate XIV., fig. 2 m, n). The 

 contents were dried up, and could not be removed and they 

 rattled about when the shell was shaken, like a pea in a whistle. 

 Evidently the history points to this — the latter two eggs were 

 long since laid, forsaken, and their contents allowed to undergo 

 dessication (which readily takes place in small eggs laid in a 

 dry situation) before another hen-bird took possession of the 

 nest and laid three eggs. If this hypothesis be accepted, it is 

 interesting to note that the hatching bird did not eject the old 

 eggs before laying ; indeed their presence may have encouraged 

 the bird to settle to the task of incubation all the more quickly, 

 as is seen in the case of domestic fowls when a china egg is 

 placed in the nesting-pen by the poultry-raiser. 



In the top row of Plate XIV., fig. 2, is an interesting example 

 of a set in which / is very sparsely spotted, and possesses a re- 

 markably clear milky-white ground-colour, reminding one more 

 of a Swallow's than a Sparrow's egg, but for the larger size. While 

 I believe this egg was laid by a different bird, it is interesting to 

 see there is a rather regular gradation in the pointing of the 

 lower pole of the set, which is best marked in /. 



It must be borne in mind that I have used the term dimorph- 

 ism in a very general, perhaps partly in somewhat an inapplic- 

 able sense. For, contrary to the case of the eggs of the Thrush's 

 nest above mentioned, which I believe constituted a genuine 

 clutch, and therefore showed dimorphism in the eggs of an indi- 

 vidual bird, in two of the cases of the Sparrows' eggs I have 

 .adopted the term dimorphism simply to indicate two very 

 different forms found occupying the same nest, but not laid by 

 the same bird. Hence while the value of the phenomenon of 

 dimorphism may here be somewhat lessened, still the differences 

 in the two types of eggs which constitute the ' false clutches,' 

 figured in Plate XIV., fig. 2, are so pronounced that, laid as 

 they have been by separate birds, these eggs seem to possess no 

 small amount of interest. 



EXPLANATION OF PLATE XIV. 



Fig. I. 



Two True-Clutches of Eggs of the House-Sparrow. (Nat. size). 



In the upper row while the eg-gs are marked very similarly, a and b are 



considerably smaller than c and d ; in the lower row, e, f, g belong- to the 



.type with a clear ground-colour with discreet blotches and spots, whereas h 



Naturalist, 



