640 THE ECHIDNA. 



the egg is very large, and that consequently there is only a partial segmentum (meroblaotic 

 type). The egg is laid at an age equal to a thirty -hour-old chick, and is enclosed in a strong, 

 flexible, white shell. The latter is three-quarters of an inch long, and half an inch broad. 

 The Ornithorhynchus lays two at a time ; the Echidna one. The former places the eggs at the 

 end of one of its burrows ; the latter in a ventral pouch." 



It seems, then, that these two mammals actually do lay eggs. The latter are hatched, in 

 one case by the warmth of the stomach-pouch in which it is carried, and in the other it is 

 dependent on the warmth of the sun or the nursing of the mother. 



. SPEAKING in the anniversary meeting of the Royal Society, in November, 1883, Professor 

 Huxley said : "It certainly is high time that British science should deal with a problem of 

 the profoundest zoological interest, the materials for the solution of which abound in and are 

 at the same time confined to those territories of the Greater Britain which lie on the other side 

 of the globe." These words had reference to the series of investigations which Mr. Caldwell 

 the first Balfour student had then gone to Australia to prosecute with regard to the embry- 

 ology of the lowest mammalian forms the monotremes and marsupials. 



Somewhat less than a year later, August, 1884, and whilst the British Association was 

 holding its meetings in Montreal, Professor Mosely, the President of the Biological Section, 

 was enabled to communicate the following brief but suggestive message from Australia : 

 "Caldwell finds monotremes oviparous, ovum meroblastic." Brief as was the message, it yet, 

 as Professor Mosely said, contained the most scientific news which had been communicated to 

 the Association in Canada. 



Zoologists will now look forward to the publication of Mr. Cald well's more detailed 

 account of his investigations. That monotremes are oviparous has been maintained by various 

 naturalists for now some sixty years, but up till the present time no sufficient evidence has 

 been brought forward to place the matter beyond dispute, the chief difficulty in elucidating 

 the problem lying in the fact that the two curious groups of animals which alone are placed 

 in the monotremata inhabit exclusively the Australian region, and hence have been studied 

 but little in their native habitat. 



Though the two are closely allied, yet the Ornithorhynchus and Echidna differ markedly 

 from each other in external appearance the one being adapted to the water, having its feet 

 webbed, and its muzzle of that peculiar shape which has earned its present title of Duck-bill 

 Platypus ; while the other is essentially a land animal, feeding on ants, which it licks up by 

 means of a long, flexible tongue, and having its body covered with sharp spines, much as a 

 hedgehog. 



The question how these animals reared their young, and in what condition the latter were 

 born, has long been a matter of much dispute, and for information we are indebted to Home, 

 Mechel, Groff, St. Hilaire, and perhaps most of all to Owen. 



In 1829, St. Hilaire laid a communication before the Royal Academy of Science in Paris, 

 in which he stated his opinion that the monotremes could no longer be admitted among the 

 mammals, nor could they be classed with birds or reptiles, but they must, though including 

 only two groups of animals, be formed into a distinct fifth class among vertebrates, the order 

 being as follows : Mammals, Monotremes, Birds, Reptiles, and Fishes. An interesting part of 

 his paper is the following: "A Mr. Holmes, while shooting on the River Hawksburgh, in 

 Australia, discovered a nest of eggs in a small burrow that the Ornithorhynchus had just left. 

 In a nest of twigs were nine eggs more than has since been credited to the creature of pecu- 

 liar shape." 



