136 TIME AND LIFE 



same in all recorded time as at present, but there are 

 particular kinds of animals and plants which have existed 

 throughout vast epochs, sometimes through the whole 

 range of recorded time, with very little change. By 

 reason of this persistency, the typical form of such a kind 

 might be called a " persistent type," in contradistinction 

 to those types which have appeared for but a short time 

 in the course of the world's history. Examples of these 

 persistent types are abundant enough in both the vegetable 

 and the animal kingdoms. The oldest group of plants 

 with which we are well acquainted is that of whose remains 

 coal is constituted ; and, so far as they can be identified, 

 the carboniferous plants are ferns, or club-mosses, or 

 Coniferre, in many cases generically identical with those 

 now living I 



Among animals, instances of the same kind may be 

 found in every sub-kingdom. The Globigerina of the 

 Atlantic soundings is identical with that which occurs in 

 the chalk ; and the casts of lower Silurian Foraminifera, 

 which Ehrenberg has recently described, seem to indicate 

 the existence at that remote period of forms singularly like 

 those which now exist. Among the corals, the palaeozoic 

 Tabulata are constructed on precisely the same type as the 

 modern millepores ; and if we turn to molluscs, the most 

 competent malacologists fail to discover any generic dis- 

 tinction between the Craniae, Lingulae, and Discinae of 

 the Silurian rocks and those which now live. Our existing 

 Nautilus has its representative species in every great 

 formation, from the oldest to the newest ; and Loligo, the 

 squid of modern seas, appears in the lias, or at the bottom 

 of the mesozoic series, in a form, at most, specifically 

 different from its living congeners. In the great assemblage 

 of annulose animals, the two highest classes, the insects and 

 spider tribe, exhibit a wonderful persistency of type. 

 The cockroaches of the carboniferous epoch are exceedingly 

 similar to those which now run about our coal-cellars ; and 

 its locusts, termites, and dragon-flies are closely allied to the 

 members of the same groups which now chirrup about 

 our fields, undermine our houses, or sail with swift grace 

 about the banks of our sedgy pools. And, in like manner, 

 the palaeozoic scorpions can only be distinguished by the 

 eye of a naturalist from the modern ones. 



Finally, with respect to the Verlebrala, the same law 

 holds good : certain types, such as those of the ganoid 



