136 BRITISH APHIDES. 



wood, at the Capo of Good Hope. It has been vari- 

 ously grouped as a Mollusc, an Annelid, and a Myrio- 

 pod. It is now shown to possess a complete tracheal 

 system. This organisation, and the characteristic 

 form of the embryo coiled within the egg, are con- 

 firmatory of the affinities now acknowledged to exist 

 between Annelida, Myriapoda, and Insecta.* Such 

 relations have been before indicated by George New- 

 port; and the illustrations furnished in Prof. Moseley's 

 memoir, and by Prof. Balfour for the Section Proto- 

 tracheata, fully bear this out from their embryonic 

 stages of development. The remark, that " Peripatus 

 points to the connection of the ringed and flat worms, 

 by means of this intermediate step, with the classes 

 only of the Arthropoda — the Myriapods, Spiders, and 

 Insects, i.e. the Tracheata," shows the importance of 

 this animal as a link in the construction of the great 

 zoological tree. 



Although superficially the hexapod larva of the 

 Centipede has a striking resemblance to some insect 

 larvas, there really is no comparison ; for, even if the 

 legs in the two are thought to be homologous, it is 

 clear by embrijolor/;/ that the insect has sprung from 

 an ancestor with numerous legs, which have become 

 atrophied ; and not from a hexapodous larval form 

 prior to the development of the full number of adult 

 appendages. + 



The morphology of Aphides has been well studied 

 by many French and German biologists, yet it may be 

 noted that, with the exception of the single memoir by 

 Prof. Huxley already alluded to, the contributions of 

 English authors have been very scanty. It is true 

 that we have a short paper on " The Ovum of Aphis," 

 by George Newport, and incidental remarks on this 

 subject are scattered through the works of Dr. W. B. 

 Carpenter, Dr. Allen Thompson, Prof. Balfour, and a 



* Balfour, chap, xvii, 'Tracheata,' p. 316. 



f Balfour, /. c, see note, vol. i, p. 323; also G. Newport, 'Phil. 

 Trans.,' ou " Myriapoda,' 1841. 



