PARTS OF INSECTS. 101 



ment on the opposite page, where it is marked with an asterisk. 



I have already pointed out how absurd such a statement would 

 appear in the case of the wood-louse ; but does it appear less so in 

 that of the cockroach ? It appears to me to be only the circum- 

 stance of the separation of the wings in the perfect insect which 

 renders it tenable at all; for in the earlier, as shown in Figs. 2 and 

 3, when the dorsal surfaces are as yet undivided, the difficulty of 

 regarding the whole breadth of the pro-thorax, as corresponding 

 with the central portion only of the next, would be as great as it 

 was in the case of the crustacean. I cannot but think, therefore, 

 that the pro-thoracic shield corresponds in its entirety, not to the 

 dorsal plate only of the next, but to that plate plus the wings ; in 

 other words, that the lateral projecting portions of this shield, 

 darkly coloured in the plate, are the homologues of the tegmina and 

 wings on the mesa- and vieta- thorax. 



I have italicised these words as containing the pith of my 

 conclusions, but the matter does not end here. If this be 

 accepted, we have a standpoint from which to view the relations 

 of the dorsal surface of the pro-thorax in other insects, the bear- 

 ing of which on the disputed question of the collar of the 

 Hymenoptera appears to me important. Again, the same reason- 

 ing will, I think, apply to the succeeding abdominal segments as 

 was used in the case of the pro-thorax. If the lateral dark-coloured 

 portions of the latter be homologous with the wings, just so will 

 be the lateral portions, also coloured dark, of the former. To 

 maintain the contrary would be as reasonable as to say that the 

 lateral portions of the first three body-segments of the wood-louse 

 were homologous with one another, and yet to refuse this charac- 

 ter to the succeeding ones ! 



Finally, the subject suggests that the whole series of projecting 

 edges of the dorsal surfaces in the crustacean are homologous 

 with the similar portions of the insect, including, of course, those 

 which on the meso- and meta- thorax are specially modified to 

 form the wings. 



I hope that some one of our entomological friends will be 

 sufficiently interested to follow out what I have said, and if my 

 reasoning is fallacious to show me wherein the fallacy lies. I fear 

 I must be open to the charge of thinking myself right and every- 



