i86 



THE DARWINIAN THEORY 



the authority of a Mr. Holmes, the eggs of Ornitho- 

 rhynchus as being ovoid in shape, equal at the two 

 ends, i \ inches long and % inch in diameter, with a 

 thin, whitish, transparent, calcareous shell. Of these 

 eggs, originally nine in number, four came to 

 England and two were deposited in the Man- 

 chester Museum, and labelled "eggs of duck-billed 

 Platypus." 



In 1884 Monotremes were shown to be oviparous 

 by Mr. Caldwell, who was sent to Australia to study 



Fig. 34. 



Embryo Chick at the end of the fifth day of incubation, showing relation 

 of embryo to yolk-sac. Typical example of a large-yolked egg. 



the subject. The Ornithorhyiichus lays two eggs at 

 a time, £ inch by \ inch in size, enclosed in a strong 

 flexible white shell ; Echidna lays only one egg. 

 The details of these eggs are not yet forthcoming, 

 but they strongly suggest affinities to reptiles. 



Osteological Evidence. — The vertebrae have no 

 epiphyses ; the sternal ribs are well ossified ; the 

 mandible is devoid of an ascending ramus ; the 

 humerus is very reptilian in character. There 



