ITS GENERAL FEATURES. 121 



Romans. The expression of human thought is not more 

 clearly indicated by the remains of these ancient civilisa- 

 tions, than the expression of creative thought is indicated 

 by the fossil forms of the palaeozoic and mesozoic Earth- 

 periods. Thus, in the palaeozoic endogens the ultimate 

 development of the leaf is, for the most part, stamped in 

 permanent beauty on the tall sculptured stems, whereas in 

 the neozoic exogens it ascends to the more exquisite but 

 evanescent beauties of the flower and fruit. Again, the 

 palaeozoic leaf, being endogenous, has a venation wholly 

 parallel, whereas the neozoic leaf adds the reticulated vena- 

 tion of the exogen to that of the endogen. Further, as the 

 floral arrangement of the endogen is formed by three, and 

 that of the exogen by Jive, all the palaeozoic flowers and 

 fruits are stamped by the normal number three, whereas 

 Jives and threes are equally normal in the neozoic flora. So 

 also in the animal kingdom : the corals of the palaeozoic 

 cycle had their septa or ray-like partitions arranged in fours, 

 while those of the neozoic are arranged in sixes. In -the 

 palaeozoic cephalopods the arms are for the most part void 

 of sucking discs, while those of the neozoic seas are, on the 

 other hand, generally furnished with them ; and in the 

 chambered shells of the same order, the palaeozoic species 

 have their sutural junctions plain and simple, while those 

 of the neozoic are often foliated and of most intricate pat- 

 tern. The palaeozoic Crustacea, even in the highest forms 

 yet discovered, are more larval-like or abdominal in their 

 segmentation than the neozoic, in which head, thorax, and 

 abdomen become distinct and definite. Again, the palaeo- 

 zoic fishes had all the heterocercal or unequally-lobed tail 

 (which marks the embryonic condition of fish-life in gene- 

 ral), while in the neozoic order, the heterocerque is subor- 

 dinated, and the homocerque, or equally-lobed, and the un- 

 divided tails become the general and normal forms. 



