350 VERTEBRATE ZOOLOGY 



homologous with a teat; the temperature of the body is lower than 

 in the higher mammals, and has a variation in health of at least 15° 

 Centigrade, a character which seems to be intermediate between the 

 poikilothermous and the homothermous conditions. 



Proechidna, a New Guinea species, differs from Echidna in the 

 following particulars: the toes on both fore and hind feet are reduced 

 to three large and two rudimentary elements; the beak is longer and 

 is curved downward; the back is more arched; the external lobe of 

 the ear protrudes freely from the hair of the head. The combination 

 of characters gives to the Proechidna a ridiculous resemblance to a 

 miniature elephant. Two species, P. bruijnii (Fig. 182, A) and P. 

 nigroaculeata (Fig. 182, B), are distinguished. 



The breeding habits of the Echinidae are of especial interest. 

 The egg is about half an inch long and has a leathery shell much 

 like that of a tortoise. Only one egg is laid at a time and it is imme- 

 diately transferred by the mouth of the mother to the brood pouch 

 (see Fig. 182, C), where it undergoes a short incubation. When 

 ready to hatch, the shell is broken, as in the bird, by means of a shell- 

 breaking tubercle on the end of the snout; the mother then removes 

 the broken fragments of shell. The just-hatched young is in a very 

 immature and helpless condition and lies quietly in the pouch for 

 some time, merely able to lap up the milky secretion that exudes from 

 the walls of the pouch. After the young has reached a considerable 

 size it is removed by the mother from time to time in order to give 

 it exercise, but it is put back into the pouch to be suckled. There is 

 among Echidnidse really no need of a nest, for the egg is kept safely 

 in a pouch. After a time, however, the mother leaves the young in 

 the burrow while she pursues her nocturnal occupation of ant-hunting. 

 This burrow with its enlarged terminal chamber is a safe retreat for 

 the youngster when later he ventures forth to learn the anteating 

 game -for himself. 



Family 2. Ornithorhynchidce.— This family consists of but the 

 single species Ornithorhynchus anatinus (Fig. 182, E), the Duck-bill 

 Platypus, a native of Southern Australia and Tasmania. When the 

 first specimen of this strange beast was exhibited in England it was 

 believed to be a fake, on a par with the composite mermaids then in 

 vogue. It was described as a furry quadruped with the bill and feet 

 of a duck; a very apt characterization. The animal is about a foot 

 and a half long, with a heavy coat of soft brown fur. The feet are 



