PLAN AND PURPOSE IN NATURE. 203 



15 At this rndimentaiy stage in tlie "development" of life 

 shone forth that Design which was never to be suspended to 

 the present time. 



16 So the azoic ages were at an end, themselves equal it is 

 thought to a third of all those that were to come. and. there 

 commenced in Pala30zoic, Mesozoic, and Cainozoic times, as 

 men call them, the formation of these successive forms of life, 

 vegetable and animal, rising from lower to higher, ever inter- 

 related and inter-dependent, with environments suited to 

 their gi'owing needs. The Age of Invertebrates found the 

 warm and quiet Laurentian, Cambrian and Silurian Seas 

 ready for their coming denizens, much as did our mammalian 

 embryo find ready a soft, vascular mucous membrane for its 

 quiet habitation and supply. The first of these three periods 

 with its two vast lines of evidence for extinct plant and 

 animal life, viz., quantities of graphite and limestone, shows 

 us the earliest annals of invertebrate history, and the immense 

 preparations made for material upon which these earliest 

 organisms must have fed, and with whicli constructed their 

 simple skeletons. The prolific outburst of marine inverte- 

 brate life in Cambrian times is very remarkable, and still 

 more in Silurian — so much so that in the Silurian all the sub- 

 kingdoms of Invertebrates, whether reckoned as eight or five, 

 were represented. This was so varied that tlie Silurian basin 

 of Bohemia alone is described by M. de Barrande as affording 

 a thousand species of Nautilus. 



17 In tlie succeeding periods of the history of the globe, 

 Devonian and Carboniferous, warmth and moisture pre- 

 vailed extensively, and the making of supplies, which 

 coming Man for his higher development would need, was 

 not neglected. The scene shifted in these ages from the 

 sea to the dry land, from the Devonian age of Fishes to 

 the long Carboniferous times. In the latter, marshy groimd 

 and peat-beds, formed after slow submergence of the land, 

 teemed with insect and reptile life, and luxuriant vegetation. 

 Ferns and club-mosses of vast size lived, died and decayed 

 into those peat-beds where the coal of various lands, of 

 European and American coal-beds, was laid down for far- 

 future use. The Mesozoic or Secondary Age, the Age of 

 Reptiles, was one of the great prolific periods of life, such as 

 that of the marine invertebrates of Cambrian and Silurian 

 times, or the Fishes in Devonian. Here was manifested a 

 remarkable development of land flora and fauna, with corre- 

 sponding outburst of marine life; crabs, gigantic sea-lizards, 



