186 SIR JOHN LUBBOCK ON PAUROPUS. 



show how greatly the most eminent naturalists have differed in opinion as to the true 

 position of the Myriapods. 



Nor ean we wonder that it should have been so. In their development the Myriapods 

 resemble Annelids, from which, however, their articulated legs and organs of respiration 

 clearly separate them. With the Crustacea they agree in possessing numerous legs ; but, 

 again, they are distinguished from them by the possession of tracheae. In this character, 

 as well as in their antennae, they resemble true insects; but the number of legs, as well 

 as the manner in which they are acquired, renders it difficult to regard them as consti- 

 tuting an order in that class. Finally, they agree with the Arachnida in the possession 

 of more than six legs, though their development and antennae are sufficient to exclude 

 them from that group also. 



We must therefore, I think, regard the Myriapoda as forming a class, separated from 

 the other classes of Annul osa by characters of at least equal importance with those by 

 which those classes are distinguished from one another. I say, of at least equal impor- 

 tance, because, while the higher families of the Crustacea and the Arachnida are clearly 

 separated by the nature of their respiratory organs, the lower ones, which have neither 

 evolutions of the external integument forming branclme on the one hand, nor invo- 

 lutions on the other, approximate in their characters so much as to render any satis- 

 factory diagnosis very difficult; so that some genera, as for instance the lienor/ on idee, 

 are actually classified by some eminent naturalists among the Crustacea, and by others 

 among the Arachnida. 



As regards the Myriapods no such difficulty has ever arisen. There is no species about 

 which there has ever been a doubt whether it belonged to that group or not. The curious 

 form described under the name of Feripatus by Guilding, may perhaps, indeed, be cited in 

 opposition to this; but although Gervais* and de Quatrefages f have expressed the 

 opinion that this genus forms an approximation to the Myriapods, the former does not 

 even mention it in his work on the Myriapods (among the « Suites h Euffon "), and the 

 absence of articulated legs is quite sufficient to remove all doubt on the point. 



Strauss Durckheim considered that Folyxenm would conduct us to the Annelids through 



Nereis, while other naturalists have regarded the Geophilidse as formin, vv . _ 



tion to the same group, and Glomeridae to the Isopods, and especially, ofcour.se, to the 

 Omscidae With Gervais and Walckenaer I regard all these resemblances as merely 

 — -ical and by no means as expressing true affinities, except, indeed, of an extremely 



g an approxnna- 



analosr 



□I 



remote character 



It is a remarkable fact, that, so far as we at present know, all Myriapods hare at first, 



ike he mite, three pairs of legs, and three pairs only. It might at first be supposed 



hat these three pairs represented those of inseets, and that other pairs were subsequently 



added on behmd-a process which in the Arachnida was arrested after the production 



of a single new pair, while in the Myriapoda it was carried on to a variable but mucl 



tllT" , fTT^ h0W6Ver ' there haS been much d »«ence of opinion as to 



the homologies of the first three pairs of legs in mites and spiders, there seems to be a 



* Aim. des Sci. Nat. 1837. + h:,. Kf A . ,. , ^ 



T Wist. Nat. des Annelcs (" Suites a Buffon "), vol. ii. p. 675. 



