396 ON THE ORDERS 



Now, if the line of analogy, beginning at the Oiihopterrf 

 for instance, and setting out for its corresponding group of 

 Thysamira, be followed, when the five circles have been 

 traversed analogically we arrive at the Homoptera^ and 

 not at the Hemiptera, which order is only attained after 

 the circles have been twice analogically traversed. This 

 may serve to explain a circumstance to which I may 

 hereafter have occasion to allude, namely, that an external 

 order* seems always to have an analogy to the two exter- 

 nal orders in the contiguous circle, but with this dif- 

 ference, that to the one it is direct and very conspicuous, 

 while to the other it is indirect and barely visible. An 

 example will best explain what is meant. The Orthoptera 

 bear a relation of analogy to both the orders of Hemiptera 

 and Homoplera, but to the former it is much more con- 

 spicuous than to the latter. The same appears to hold 

 good with all the other external orders. 



To follow up these speculations at present would be 

 losing sight of the principal object which it was originally 

 our purpose to keep in view. It need only, therefore, be 

 stated, that when we shall have once attained a knowledge 

 of the accurate series of affinity, the study of relations of 

 analogy seems calculated to throw hght on almost every 

 general and specific notion, that may have been or can be 

 entertained on the nature of these animals. To those who 

 may have a taste for this investigation it must, for tlie pre- 

 sent, be left, while our attention shall be more closely con- 



* By an external order is meant any one situated in the greater segment 

 of a circle of affinity, when divided by a line joining its osculant points. 

 There are ten such, viz. Orthoptera, Neuroptera, Homcptera, Hemiptera, 

 Phalangidia, Scorpionidea f Amphipoda f Lcemndipoda f Chilnpoda and 

 Thysanura. We may name the five orders, Fermes, Hymenopiera, Diptera, 

 jicuTidea, and Branchinpnda, internal, and the ten remaining inosadant, 

 from their communicating with osculant groups. 



