24 



THE BRITISH NATURALIST. [February 



back amongst the bygone ages in search of the ancestors of birds, till 

 we came to the border-land of vegetable and animal life, when, ap- 

 parently, our earth was only fitted to be the habitation of such lowly 

 organisms as the protists ; but this would detain us too much, and if 

 we begin with the earliest fossil reptile, it will be quite enough for 

 our purpose. . 



In attempting to discover the origin of birds, our researches will 

 conduct us to the ultimate question of the origin of life. It must, 

 however, suffice to say that, so far as we know, life always comes from 

 pre-existing life, i.e., we have no experience of what has been called 

 spontaneous generation, and our knowledge tends to shew that all 

 living forms have descended from a simple primitive form, and that 

 you and I are, in a sense, a part and parcel of that first life which 

 started on our globe aeons ago. 



With the doubtful exception of Archegosaurus, and one or two allied 

 forms which may be regarded as transitional from the Batrachians, 

 reptiles first appeared in the Permian epoch. These earliest reptiles 

 were lizards, and from these distant ancestors there has been an unin- 

 terrupted chain of descent to our existing reptiles and birds. This 

 may seem a large assertion, but it is a true one. As previosly stated, 

 the first indisputable traces of true reptiles occur in strata of Permian 

 age, and here it may not be out of place to lay stress on the enormous 

 lapse of time w^hich each geological period represents. Some of these 

 periods may be measured by tens of thousands, but most of them by 

 hundred of thousands of years. As an illustration it may be taken as 

 absolutely certain that those who estimate the duration of the carbon- 

 iferous period alone at 120,000 years are very much below the mark. 



The remains of reptilian life found in rocks of Permian age are not 

 nearly so varied and extensive as those of succeeding periods, such as 

 have been found make it certain that reptiles of types presenting 

 marked variations from those of the previous Permian age were in 

 existence ; and in the more extensive reptilian remains of the next 

 period, these variations are still further developed, and we find forms 

 diverging very considerably from those of their Permian ancestors. It 

 may perhaps make this more clear if I mention that the few land 

 lizards of the Permian are succeeded in the Triassic period by con- 

 siderably modified forms of land reptiles, and also by some most 

 extraordinary marine reptiles, such as Ichthyosaurus and Plesioraurus, 



