"NOTE ON THE HOMOLOGIES OF INSECTS. Till 



other ; as well as by the fact that the ganglia of the mouth seg- 

 ments (my oesophageal and oral ganglia) are anterior to the ganglia 

 of the eyes and antenna: and that the optic and antennal seg- 

 ments ore developed from iniaginal discs, contiguous with those 

 of the thorax. I give them for what they are worth and must 

 leave those, who know the homologies of the arthropods generally 

 better than I do, to judge whether the facts are sufficient to jus- 

 tify my conclusions. It is true Dr. Weismann has named certain 

 lobes, which he has found in the embryo larva, behind the an- 

 tennal and optic segments, maxillary and mandibular segments ; 

 but I do not think any connection can be traced between these 

 lobes and the organs of the mouth. I confess, however, I have 

 never been able to distinguish them. 



With regard to the thorax if any substantial homology can be 

 traced between it and any of the segments of the Crustacea, I 

 should be inclined to look upon it as the homologue of the mid- 

 dle-body* of the latter from its late development in the fly, and 

 from its bearing the ambulatory legs. 



I have stated, inadvertently in a note, on page 3, that " seven- 

 teen segments is the number assigned on theoretical grounds to 

 all true insects" but no sufficiently stable theory has, pehaps, 

 been formed to justify the expression : and I find, according to 

 Gerstacker, that the Orthopterahave eleven abdominalsegments, 

 forming an exception to the number I have given. 



I find I agree with M. Duthiers, in describing the opening of 

 the sexual organs between the eighth and ninth abdominal seg- 

 ments, but did not see the great importance of the observation 

 at the time I made it. Lastly, strangely enongh, I have made use 

 of an expression in the second paragraph on page 7 which is iden- 

 tical with one used by Sir John Lubbockf in his paper on the 

 development of Ephemera, although I did not know at the time, 

 that it had been previously used. 



* 1 use this term as it is used by F. Muller in his "Facts for Darwin " 

 translated by Dallas. 



f Linn. Soc. trans, vol, xxv. page 489. 



