400 



University of California. 



[Vol. 3. 



similar to those now obtaining' ducks would be much more 

 numerous than any of the other possible forms, and the proba- 

 bilities, therefore, favor its anatine origin. Considering that 

 great individual variation often occurs in a single set of eggs, it 

 is evident that specific conclusions as to the parentage of any 

 specimen can hardly be drawn from form alone. 



THE CONTENTS. 



With the exception of a small space near the periphery, the 

 interior of the egg is filled solidly with a beautifully crystalline 

 mass of the mineral colemanite (PI. 49, fig. 1). In several 

 places next the shell there is present a dark brown semi-fluid 

 tarry material (PI. 49, fig. 1, t) resembling asphalt in appearance 

 and physical properties. When cold it is brittle, showing a 

 conchoidal fracture with brilliant surfaces, the edges of the 

 fracture becoming rounded on standing. As the temperature 

 rises it grows softer, until at 100° C it becomes a fluid with 

 considerable viscosity. Its specific gravity is a trifle less than 

 that of boiling water. It is readily and completely soluble in 

 petroleum ether, carbon disulphide and chloroform. Hence it 

 resembles very closely that fraction of natural asphalts which has 

 been known as "petrolene." 



Between 150° and 250° C a far-reaching decomposition takes 

 place, resulting in the liberation of relatively large volumes of an 

 inflammable gas. Of the residuum in the ignition tube after 

 such treatment, about fifty per cent only is soluble in petroleum 

 ether. The greater part of the remainder dissolves in carbon 

 disulphide, but an appreciable residue is soluble only in chloro- 

 form. It is thus evident that the substance obtained after 

 heating cannot be differentiated from a natural asphalt, since it 

 may be separated into the so-called "asphaltene," as well as the 

 "petrolene" fraction, by the ordinary methods. 



Submitted to ultimate analysis the same similarity is apparent. 

 Qualitatively examined the tar shows the presence of carbon, 

 hydrogen and sulphur, but not of nitrogen, and although, as it 

 occurs in the egg, the tar contains apparently a smaller percent- 

 age of carbon than is found in asphalts generally, the heated 



