( Ixix ) 



sary for the preservation of vast numbers of species belonging 

 to different orders, the structural differences between which 

 are of course precise. And here we may perhaps pass on to 

 the consideration of quite a different subject, which is sug- 

 gested to us by the mention of the precision of these structural 

 differences ; how did they arise 1 how were they established 1 

 and, above all, how were they differentiated to preciseness at 

 such early geological periods 1 With regard to the first origin 

 of the Insecta we know absolutely nothing : it has been the 

 custom for some time to pre-suppose that they originated in 

 some single form such as Campodea, which, according to 

 Haeckel, should be looked for above the Silurian rocks, but this 

 is pure hypothesis, and has not a single fact in the geological 

 record to support it : " the Silurian cockroach," as INfr. Goss, 

 who has done so much good work on the subject, says, 

 " though differing in detail from any existing or extinct form, 

 is, in its imago state, as far removed from the hypothetical 

 ancestral form, as any existing representative of the class. 

 Of course it does not follow that an ancestral form may not 

 be discovered, and Packard considers that the larval cockroach 

 bears a strong resemblance to Lepisma (a genus of Thysanura), 

 and therefore the Orthoptera are descended from Thysanura^ 

 Avhich latter order comprised the lost type, from which the 

 lusBcta, in the main, drew their origin," * 



The earliest known insects belong to the Ortlioptera, 

 Neurop)tera, and Bemiptera, and to an extinct ISTeuropteroid 

 order, raltvodictyoptera : the types were strongly differentiated 

 even in the earliest times, but the structure appears to have 

 been more homogeneous in some respects. Sir John Lubbock 

 (now Lox'd Avebury), writing in 1876 on some of the early 

 insects, says that, although in some respects less specialised 

 than existing forms, they " are as truly and as well charac- 

 terised insects as any now existing ; nor are we acquainted 

 with any earlier forms which in any way tend to bridge over 

 the gap between them and the lower groups." This is pre- 

 eminently true of the Coleoptera, which from the time of 

 their first appearance in geological strata have practically 



* "On some recently diseuveicd luseeta from Carboiiifeious aud Silurian 

 Rocks," by Herbert Goss, 1885. 



