Septembee 2. 1898.] 



SCIENCE. 



28& 



The effect of the Appalachian revolution 

 and corresponding phj'sical changes in 

 Europe was by no means disastrous to the 

 Stegocephala, for those of the Liassic, where 

 the conditions must have been more formid- 

 able to terrestrial vertebrate life, were 

 abundant, and in some cases at least colos- 

 sal in size. Whether the salamanders, cce- 

 cilians, sirens and Amphiuma of present 

 times are persistent types, survivors of Car- 

 boniferous times, or whether the process of 

 modification has been accomplished a sec- 

 ond time within the limits of the same class, 

 is perhaps a matter for discussion. 



Besides the introduction and elaboration 

 of the air-breathing, four-footed labyrintho- 

 donts, the sloughs and sluggish streams 

 were alive with Naiadites and its allies, 

 forerunners of the Unionidse, and with them 

 lived shelled Phyllopods, Estheria having 

 already appeared in the Devonian, Leaia 

 appearing in the Carboniferous ; and also 

 the larvae of aquatic net-veined insects, 

 fragments of the imagines of which were 

 detected by Hartt at St. John, New Bruns- 

 wick. 



The coal-bearing strata are largely fresh- 

 water beds of fine shale and well calculated 

 to preserve the hard parts of delicate ani- 

 mals, but on general grounds it is evident 

 that the great extent of low lands with ex- 

 tensive bodies of fresh water, communica- 

 ting with the shallow sea, was most favor- 

 able to the development and differentiation 

 of terrestrial life. Though fresh-water and 

 land shells (pulmonates) appeared in the 

 Devonian, they were apparently more 

 abundant in the coal period. Especially 

 rapid was the incoming of the arthropods ; 

 both diplopods, some of them very remark- 

 able forms, and chilopods lived sheltered 

 under the bark of colossal lycopods ; with 

 them were associated scorpions, harvestmen 

 and spiders. The great profusion of net- 

 veined insects discovered at Commentry, 

 France, shows that this was the age of the 



lower more generalized or heterometabolous 

 insects, such as cockroaches and other Or- 

 thoptera, of Eugereon, may-flies and pos- 

 sibly dragon-flies, etc., our wingless stick- 

 insects being then represented by winged 

 ancestors. At this time also began the ex- 

 istence of insects with a complete metamor- 

 phosis, as traces of true Neuroptera and the . 

 elytra of a beetle have been detected in 

 Europe. But thus far no relics of flowers 

 or of the insects which visit them have been 

 discovered in Carboniferous times, not even 

 in the Permian, so that the origin of insects 

 with a complete metamorphosis, such as 

 moths, ants and flies, may be atti-ibuted to 

 the new order of things, geographical and 

 biological, immediately following the Ap- 

 palachian revolution. 



We do not wish to be understood as im- 

 plying that the origin of new orders and 

 classes is directly due to geological crises or 

 cataclysms themselves.* On the contrary, 

 the initial steps seem to have been taken as 

 the result of the gradual extension of the 

 land masses and the opening up of new 

 areas ; it was the period of long preparation, 

 with long-continued oscillations, the slowly 

 induced changes resulting from the reduc- 

 tion of the mountainous slopes to pene- 

 plains, which were most favorable to the 



* I find that Wood has already expressed the same 

 idea more fully, as follows : "Both in the palaeozoic 

 and secondary periods, therefore, the complete changes 

 in the fauna which marked their termination do not 

 appear to have been immediate upon the changes of 

 the geographical alignement, but to have required the 

 lapse of an epoch for their fulfilment ; and the com- 

 pleteness of that change is perhaps not less the in- 

 direct result of the altered alignement, by the forma- 

 tion of continents where seas had been, and the 

 opening out of new seas for the habitation of marine 

 animals, thereby cairsing a gap in the geological rec- 

 ords so far as they have been hitherto discovered, 

 than the direct result of the changed conditions to 

 which the inhabitants of the seas, and even those of 

 the land, came to be subject on account of the entire 

 change in the alignement of the land over the globe." 

 {Phih Mag., XXIII., 1863, p. 281.) 



