218 ON SYSTEMATIC ZOOLOGY. 



thrown great uncertainty on his circles of Ametabola 

 and Crustacea, but alters the position of every group in 

 the diagram. If, on the other hand, we are to believe 

 that the positions of these groups in the annulose dia- 

 gram is correct, then that of the Mandibulata * must be 

 reconstructed ; for the Thysanuriform type cannot be at 

 once both typical and aberrant ; nor can the ChilognatM- 

 form Ametabola be aberrant, and the Chilognathiform 

 Coleoptera typical. We are convinced, therefore, that 

 this talented author had not ascertained the fact, that 

 the denomination of a group is always definite ; that is 

 to say, it is either always typical or always aberrant : 

 he justly supposes that the contents of one natural 

 group represent the contents of another natural group; 

 but he did not perceive that one of the consequences of 

 this fact was, that the divisions which were typical in one 

 would be typical in another; for if otherwise, the parallel 

 between the two would fail. This oversight, in fact, 

 has not only proved the artificial nature of the ame- 

 tabolous circle, but has been no small source of em- 

 barrassment to the attempt of arranging the order 

 Lepidoptera in conformity therewith. Every entomo- 

 logist must perceive that the two typical (or external) 

 divisions of the diurnal butterflies, as Shrank and the 

 authors of the Vienna Catalogue long ago intimated, are 

 represented by the genera Nymphales and Papilio; the 

 first being the Chilopodiform stirps of Dr. Horsfield, 

 and the latter the Chilognathiform : but if the series of 

 the Ametabola is to be adhered to, as given in HOT. Ent. 

 p. 390., then this theory must be altogether abandoned; 

 the genus Morpho, as corresponding to the Thysanura, 

 must be a typical group ; that of Nymphales, the other ; 

 while that of Papilio becomes aberrant, leading directly 

 out of the circle ! It is clear, therefore, that if, as many 

 passages in his work indicate, our learned author enter- 

 tained a suspicion that the rank of his groups was de- 

 finite, he did not believe that this property was univer- 



* Hor. Ent. p. 439. 



