Appendix I 



18 



7 



the impossibility of exact description. Only, indeed, by means of micro-photography would it be possible 

 to render the descriptions intelligible to oologists other than specialists. 



As I have said, almost imperceptible differences of structure in the shells of the eggs of closely 

 related birds cannot be expressed by words alone. To describe the characters of the eggs of a whole group 

 (genus) to a certain extent is indeed possible, but in describing a separate species one has to be satisfied in 

 the majority of cases with a remark like " the egg of this species, while possessing all the characters of the 

 group, has a coarser or rougher surface, in which are absent or present the pores, which in their turn are 

 deeper or shallower, broad or narrow," and so on. 



Having taken an egg with such extreme characters as the point of departure, the eggs of other 

 species can only be compared with it in proportion to the more or less marked resemblance of their grain 

 to one another, and to that of the fundamental form. Such comparisons are, however, only possible when 

 you have types before you ; in the absence of these, or, at any rate, of micro-photographic impressions, 

 the best assistance for the determination of closely related eggs of one colour is afforded by tables, which 

 allow of the comparison of the weight of the eggs (i.e. shells) of various species possessing either 

 approximate or equal dimensions. In the annexed table, what at once strikes the eye is the fact that the 

 weight is much more nearly correlated with the breadth than with the length of the egg, and that it is also 

 in close connection with the structure of the shell, the outward sign of which is its grain. 



From their external appearance alone, the extremely solid, hard shell of the eggs of Anser anser, 

 Eul. indica, and С cygnoides, coupled with their greater weight, allows of their easy distinction from the 





TABLE OF WEIGHT, BREADTH, 



AND LENGTH OF EGGS OF ANSERINE 





Weight in Centigrammes. 



Breadth 



Length 



xAiis. anser. 



Melanonyx 



Breadth 



Length 





Melanonyx 



Melanonyx 



Cygnopsis 



Eulabeia 



in mm. 



in mm. 





segetum. 



in mm. 



in mm. 





segetum. 



arvensis. 



cygnoides. 



indica. 



65 



87 



X 





59 



90 



23IO 











64 



85-5 



2244 







88 



I866 











63-5 



95-5 



2352 







87 



. 2142 





. . . 









88.5 



2352 







86.5 



I980 





. . . 







63 



94 

 89-5 



89 



2430 



2400 

 f 2382 | 

 \ 2442 J 



: 





86 

 84 



83-5 





1500 



1320 



1512 



... 



62.5 



9°-5 



2076 







83 



1698 











62 



94 



91 



89 



88.5 

 86.5 



84-S 



2214 

 2040 

 2172 

 2010 

 i860 

 1938 



1680 



58.5 



81 

 76 

 89 

 88 

 86 



85 



183О 

 2052 

 1932 

 1776 



1440 



... 



1512 



... 



61.5 



89-5 

 87-5 



2004 

 2130 







84-5 

 84 



I716 



... 



1278 X 



... 



1422 



61 



95 

 92 



91 



90 



88.5 



87-5 



2298 



2004 



f 2112 ) 



1 T 932 j 

 2004 



J 95o 

 1914 



... 



58 



78 

 89-5 



87-S 



87 

 86 



85 



2022 



1692 

 I908 



1536 



1338 



1572 



... 



60.5 



89-5 

 88.5 



2052 

 1902 







84 

 83-S 





1500 



1248 



f із°8 ) 

 1 1278 j 



... 



























85 



2172 







82.5 



l842 



1398 







1392 



60 



87.S 



1980 







80 



. . . 



. • . 



1212 



. . . 



• • . 





86 



X 





57-5 



87-S 



. . . 







1560 





59-5 



9°-5 

 37-5 

 85-5 

 85 



1944 



1890 



1830 



1476 





35 

 83 

 81.5 



1878 



X 



X 



... 



... 



