4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 



The Egg 



Figures i, kt (Plate I) 



The egg (fig. i) is a perfect ellipse, the relative lengths of whose 

 axes vary considerably in the eggs of different nests and slightly in 

 the eggs of the same nest. Of more than four hundred eggs meas- 

 ured, the longest was 85 mm. ; the shortest 65 mm. Of the same 

 eggs, the greatest short diameter was 50 mm. ; the least short diam- 

 eter was 38 mm. The average long diameter of these four hundred 

 eggs was 73.74 mm. ; the average short diameter was 42.59 mm. 

 The average variation in the long axis of the eggs of any one nest 

 was 11.32 mm., more than twice the average variation in the short 

 axis, which was 5.14 mm. No relation was noticed between the size 

 and the number of eggs in any one nest. Ten eggs of average size 

 weighed 812 grams — about 81 grams each. 



Voeltzkow (18) 1 states that the form of the egg of the Madagas- 

 car crocodile is very variable. No two eggs in the same nest are 

 exactly alike, some being elliptical, some "egg-shaped," and some 

 "cylindrical with rounded ends." The average size is 68 mm. by 

 47 mm., shorter and thicker than the average alligator egg. 



When first laid, the eggs are pure white, and are quite slimy for 

 a few hours, but they generally become stained after a time by the 

 damp and decaying vegetation composing the nest in which they are 

 closely packed. 



The shell is thicker and of a coarser texture than that of the hen's 

 egg. Being of a calcareous nature, it is easily dissolved in dilute 

 acids. 



The shell membrane is in two not very distinct layers, the fibers of 

 which, according to S. F. Clarke, are spirally wound around the egg 

 at right angles to each other. No air-chamber, such as is found in 

 the hen's egg, is found in any stage in the development. 



In most — probably all normal — eggs a white band appears around 

 the lesser circumference a short time after being laid. This chalky 

 band, which is shown at about its maximum development in fig. 

 la, is found, on removal of the shell, to be caused, not by a change 

 in the shell, but by the appearance of an area of chalky substance in 

 the shell membranes. Clarke thinks this change in the membrane is 

 to aid in the passage of gases to and from the developing embryo. 

 Generally this chalky area forms a distinct band entirely around the 

 shorter circumference of the egg, but sometimes extends only partly 



1 The numerical citations throughout the article are to bibliographical refer- 

 ences at the end of the paper. 



