64 



NATURE 



\Nov. 23, 1871 



preaching when difficulties may be brought under con- 

 sideration and discussion. 



"There are," Sir John Lubbock remarks, "peculiar 

 difficulties in those cases in which, as among the Lepidop- 

 ttra, the same species is mandibulate as a larva, and suc- 

 torial as an imago." The power of mastication during 

 the first period of life being an advantage, on account of 

 a certain kind of food being abundant, and that of suction 

 duringthe second, when another kind of food prevailed, or 

 vice tv;-j(?, is suggested as a possible txplanation of the 

 origin of species which are mandibulate during one period 

 of life and not during another. In such cases it is said we 

 have " two forces acting successively on each individual, 

 and tending to modify the organisation of the mouth in 

 different directions." It is suggested that the change from 

 one cordition to the other would take place " contempo- 

 raneously " with a change of tkin. Then it is urged that 

 even when there is no change of form, the softness of the 

 organs precludes the insect from feeding for a time, and 

 when any considerable change was involved, " this period 

 of fasting, it is remarked, would be prolonged, and would 

 lead to the existence of a third condition, that of pupa, in- 

 termediate between the other two." 



Theie is much that is assumed in this reasoning ; but I 

 shall now venture to call the attention of naturalists to one 

 point only, namely, the analogy between the period of 

 fasting caused by the temporary softness of the organs 

 while the caterpillar changes its skin, and the more pro- 

 longed fasting period when the organs undergo that more 

 considerable (!) modification involvedinthechangefromthe 

 mandibulate to the suctorial type of mouth. The change 

 from a small mandibular apparatus to a larger one seems 

 to be compared with the change from a mandibular to a 

 suctorial apparatus — the change of skin of the caterpillar 

 with the change of skin when the caterpillar becomes the 

 pupa, and the latter the imago — the temporary softness 

 which prevails when the little mandibles grow into bigger 

 mandibles, with the temporary softness which prevails 

 while the mandibles become convened (!) into the suctorial 

 mouth. But these changes are surely of diffeient orders, 

 and the operations of a different nature. The mandibles 

 do not change. The one type of mouth does not pass 

 through gradations of any kind into the other kind of 

 mouth. But one abruptly ceases, its work having been 

 discharged, while the other is developed anew. As com- 

 pared with the change of skin of the caterpillar, the change 

 of skin from chrysalis to butterfly is indeed a " consider- 

 able chain^e." It w-ould require an amazing intelligence 

 to premise from the study of a caterpillar that from it, 

 after certain changes of skin and periods of rest, would 

 emanate a butterfly. 



It is very well to suggest that " in reality the neces- 

 sity for rest is much more intimately connected with 

 the change in ihe constitution of the mouth"; but 

 what, I would ask, is the evidence of the connection 

 implied ? Between the change from the small man- 

 dibles to the large, and the change from the latter to 

 the suctorial apparatus, there can be no comparison— no 

 analogy, for the suctorial mouth is developed anew during 

 the pupa state, and its formation is not commenced until 

 all traces of the mandibles are gone. Nay, every tissue 

 of the caterpiUar disappears before the development of 

 the new tissues of the imago is commenced. The muscu- 

 lar and nervous systems of the latter are as different from 

 those of the former as are the digestive apparatus, the oral 

 mechanism, and the external covering. These organs do 

 not change fiom one into the other ; but one, having per- 

 formed its work, dies, and is removed entirely. Not a 

 vestige of it remains. Its place is occupied by formless 

 living matter, like that of which the embryo in its early 

 stages of development is composed ; and from this form- 

 less matter are developed all the new organs so marvel- 

 lously unlike those that preceded them ; and others 

 unrepresented at all in the larval stage, make their 



appearance. To explain, according to Mr. Darwin's 

 theory, the " period of change and quiescence " inter- 

 mediate between the caterpillar and imago states of 

 existence, is likely to remain for some time a very 

 difficult task. If the difficulty cannot be resolved until 

 the period of quiescence during which the imago is 

 formed, is proved to be analogous to the periods of quies- 

 cence during the change of skin of the larva, the life 

 history of a butterfly will remain for a long time a puzzle 

 to Mr. Darwin and those who believe in the universal ap- 

 plication of his views. Lionel S. Beale 



ON THE RECURRENCE OF GLACIAL PHE- 

 NOMENA DURING GREAT CONTINENTAL 

 EPOCHS 



IN the August number of the Geological Society of 

 London I published two papers " On the Physical 

 Relations of the New Red Marl, Rha?tic Beds, and 

 Lower Lias," and " On the Red Rocks of England of . 

 older date than the Trias." In the latter I attempted to 

 prove that for the north of Europe and some other parts 

 of the world, a great Continental epoch prevailed between 

 the. close of the upper Silurian times and the end of the 

 Trias or commencement of the deposition of the Rhastic 

 beds; in other words, that the Old Red sandstone. Carbo- 

 niferous strata, Permian beds, and New Red series were 

 chiefly formed under terrestrial conditions, all, with the 

 exception of the Carboniferous series, in great lakes and 

 inland seas, salt or fresh. 



The Permian strata, in particular, appear to have been 

 deposited under conditions to which the salt lakes in the 

 great area of inland drainage of Central Asia afford the 

 nearest modern parallel. 



While brooding over the whole of this subject for several 

 years past, I have often been led to consider its bearing 

 on those recurrent phenomena of glacial epochs which 

 now begin to be received by many geologists. 



The phenomena of moraine-matter, scratched stones, 

 and erratic boulders, whether deposited on land by the 

 agency of glaciers, or in the sea and lakes by help of 

 floating ice, are evidently intimately connected with the 

 contemporary occurrence of large areas of land, much of 

 which may, or probably must, have been mountainous. 



The late Mr. Cumming, in his History of the Isle of 

 Man, " hints at the glacial origin of certain Old Red conglo- 

 merates in that island, conceiving that the bony external 

 skeletons of some of the fish of the period may have been 

 provided to enable them to battle with floating ice. In 

 lectures and in print I have frequently stated my belief 

 that the brecciated subangular conglomerates and boulder 

 beds of the Old Red sandstone of Scotland and the north 

 of England are of glacial origin, so distinct, indeed, that 

 when these masses and our recent boulder clay come 

 together, there is often actual difficulty in drawing a line 

 of demarcation between them. I frequently felt this diffi- 

 culty )ears ago, when, commencing the Geological Survey 

 of Scotland, I mapped the strata in the country south of 

 Dunbar, and the same difficulty was occasionally felt by 

 others in the valley of the Lune, near Kirkby Lonsdale. 



If, as I believe, the Old Red sandstone was deposited 

 in inland Continental waters, the Grampians, as a moun- 

 tain tract, bordered these waters, and they must have been 

 much higher then than now ; not only because of the 

 probably greater elevation of the whole continent, but also 

 because tlie Grampians formed land during the whole of 

 the Upper Silurian epoch, and suftered great waste by 

 denudation, then and ever since. The glaciers of these 

 mountains marked an episode in Old Red sandstone 

 times, and yielded much of the material of the boulder 

 beds of the Old Red sandstone. 



In these regions and in North America, the Carboniferous 



