SCIENCE- GOSSIP. 



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requiring so great an increase of this irrespirable 

 gas to explain the warm and uniform climate of 

 earlier geological epochs, as to have rendered the 

 atmosphere fatal to all animal life. Basing his 

 calculations on the result of researches by 

 Fourier, Tyndall, Pouillet, LangJey, Paschen, Knut 

 Angstrom, and other workers, the eminent 

 Swedish meteorologist, Svante Arrhenius ( 6 ), has 

 been able to present the matter to us in quite a 

 different light. The later invaluable contribution 

 to the subject by Dr. Nils Ekholm ( 7 ), has still 

 further served to acquaint us with the very slight 

 variation necessary in the apparently insignificant 

 amount of carbonic acid now present in the 

 atmosphere, to change our present climate to that 

 of the Great Ice Age, or to give to the arctic 

 regions the genial warmth of the temperate 

 zone. 



Although fossils had attracted attention from 

 very early times they were formerly regarded more 

 as "freaks of nature" than as links with the past, 

 and it was left for the celebrated French natu- 

 ralists, Buffon and Cuvier, to first direct serious 

 attention to them, the study of insect palaeontology 

 being shortly afterwards taken up by Marcel de 

 Serres. The first publication dealing with purely 

 British fossil insects was Broclie's ( 8 ) monograph, 

 whilst for our knowledge of the ancestral develop- 

 ment and evolution of the cockroach in particular, 

 we are more especially indebted to the indefati- 

 gable labours of the eminent American phytogenist, 

 Samuel H. Scudder (°). Almost the whole of our 

 knowledge of these earlier types has been derived 

 from the wings, the membranes and veins of which 

 are sometimes preserved with astonishing per- 

 fection. From these we learn that although 

 through the long eons of time that have elapsed 

 the general form and appearance of the Blattidae 

 have altered little, existing species differ from 

 their earliest ancestors in detail. For whereas in 

 modern cockroaches the anterior pair of wings has 

 become modified into tough protecting covers or 

 tegmina, in archaic forms all four of these thoracic 

 appendages were alike in structure and equally 

 transparent. The number of main veins, too, in 

 these antique species were the same in all the 

 wings, whereas in existing members of the group, 

 two or more have blended in the anterior pair and 

 thus stiffened them for shielding purposes. Having 

 thus briefly contrasted our earliest and latest 



(6) " On the Influence of Carbonic Acid in the Air upon the 

 Temperature of the Ground." 



(7) On the Variations of Climate of the Geological and 

 Historical Past and their Causes, " Quart. Jour. R. Met. Soe." 

 1901. (For recent publications bearing on earlier climate gene- 

 rally see also Harmer, On the Influence of Winds upon Climate 

 during the Pleistocene Epoch, " Jour. Geol. Soc," 1901 ; Phip- 

 son, " Researches on History of Earth's Atmosphere," 1901.) 



(8) " History of the Fossil Insects in the Secondary Rocks of 

 England," P. B. Brodie, Lond. 1845. 



(9) " Palaeozoic Cockroaches," Boston, 1879 ; " Review of 

 Mesozoic Cockroaches," Boston, 1886 ; " The Cockroach of the 

 Past," London, 1886. 



insects, it will prove of interest to refer in passing 

 to the intermediate or Mesozoic types, which we 

 may, perhaps, as a whole be allowed to claim as 

 " connecting links," for although some few show 

 little alteration from the archaic form, in a by no 

 means inconsiderable portion, the venation of the 

 tegmina exhibits a distinct advance approximating 

 to that of our modern cockroaches. 



Nearly seventy species have been found in Eng- 

 land, principally from the Purbecks of Wilts and 

 Dorset, and the Upper and Lower Lias of Gloucester- 

 shire, Warwickshire, and Worcestershire ( ,0 ). The 

 Coal-measures of Commentry in France have yielded 

 over six hundred specimens of cockroaches, whilst 

 many more have been recorded from the rich 

 fossiliferous Carboniferous Kocks of Switzerland 

 by Heet, who states that during this geological 

 period they were unquestionably the most widely 

 distributed and abundant of all our insects. 

 This opinion is fully endorsed by Scudder, who 

 says " they [cockroaches] so far outnumber all 

 other types of insects that this period, so far as its 

 hexapodal fauna is concerned, may fairly be called 

 the ' age of cockroaches ' " ( n ). It has been noted 

 that the average size of specimens from the British 

 Oolites is less than those from the Lias, which in 

 turn are slightly smaller than those from the 

 underlying Triassic beds. That is to say, so far 

 as our British fossils are concerned, the farther we 

 go back in time the larger do our cockroaches ap- 

 pear to have been. In a paper on fossil insects 

 generally, read before the Warwickshire Naturalists' 

 and Archaeologists' Field Club at Warwick in 1889, 

 the president, the Bev. P. B. Brodie, said : " There is 

 a great difference between the Purbeck insects in 

 the two chief localities in Wilts and Dorset, where 

 they 'occur most frequently. In the limestone in 

 the former, which contains the Middle Purbecks, 

 they are much better preserved, with the wings 

 and other parts of the body attached, though the 

 wings are rarely expanded. In the latter county 

 they are generally in masses, often covering the 

 slabs of stone, much broken up, wings and elytra 

 of beetles with other parts of insects lying thick 

 together, but entire insects are extremely rare. 

 The mode of deposit in these two cases must have 

 varied considerably " ('-), In treating of the fossil 

 insects of Bavaria, Dr. Hagan has called attention 

 to the perfect state of preservation of the majority 

 of specimens from that part of Germany, from 

 which he infers both a proximity to land and slow 

 precipitation of sediment at the time they were 

 embedded. Whether any such factor could have 

 contributed to mark the difference between our 



(10) P. B. Brodie, " On the Prominence and Importance of 

 the Blattidae in the Old World " (1889) ; see also H. Woodward, 

 " Some new British Carboniferous Cockroaches " (1887) and 

 " On a Remarkable Fossil Orthopterous Insect from Scotland." 



(11) " The Cockroach of the Past." 



(12) P. B. Brodie, " On the Character, Variety, and Distri- 

 bution of Fossil Insects in the Palaeozoic, Mesozoic, and Caino- 

 zoic Periods." 



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