xxv] 



PROTOTHERIA 



657 



There is no teat, but the fluid from the milk-glands seems to soak 

 into the hair and thence is sucked by the young. Before binh 



FIG. 325. 



Fio.326. Diagram to illus- 

 trate the arrangement of 

 the female genital ducts 

 in the Pro'totheria. 



1. Ovary. 2. Oviducal 

 funnel. 3. Oviduct. 

 4. Opening into cloaca. 



S. & M. 



The Duckbill, Ornithorhynchus anatinus. 



the young receive a certain amount of 

 nourishment from the mother but the egg 

 does not become adherent to the wall of the 

 oviduct. The egg of Echidna for instance 

 swells from a diameter of 2 millimetres to 

 a diameter of 4 millimetres and more in its 

 passage through the oviduct. A consider- 

 able amount of food is supplied by the 

 abundant yolk in the egg. After birth 

 the egg is carried by the female Echidna 

 in a ventral pouch of skin on the abdomen. 

 The female Ornithorhynchus has no such 

 pouch. 



The skeleton of the Prototheria pre- 

 sents many interesting features of agree- 

 ment with the Reptiles ; thus the vertebrae 

 have no epiphyses, and there is not only 

 a complete coracoid articulating with the 

 sternum, but also two precoracoids which 



42 



