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X. Morphological Notes hearing on the Origin of 

 Insects. By J. Wood-Mason, F.G.S., F.L.S., 

 F.Z.S., Deputy Superintendent, Indian Museum, 

 and sometime Professor of Comparative Anatomy, 

 Medical College, Calcutta. 



[Read May 7th, 1879.] 



1§. TiiEiR position relative to the eyes* and mandibles 

 seems to point to the antenna) of 3Iachilis as being homo- 

 logous with the antenna; (III) proper of Crustacea. These 

 appendages are, in 31. maritima,'\ composed, as usual, of a 

 peduncle and of a flagellum : the former consists of a 

 single joint, which is rather broader than long, and slightly 

 enlarges from its insertion to the end of the basal third, 

 where it is thickest, and where a conspicuous sutural mark 

 shows that it is made up of two primitively distinct and 

 separate joints ; near its apex, on the inner and inferior 

 side, arises a short conical process, terminating abruptly 

 in a small blunt papilla, from which spring one or two 

 hairs. When the insect is at rest, the antennas are laid 

 back upon the sides of the thorax, bending at the junction 

 of the peduncle with the setaceous subsegmented flagellum; 

 the first joint of this — little more than half the thickness 

 of the peduncle — is of uniform breadth throughout, almost 

 twice as broad as long, its breadth being to its length as 

 8 : 5 about, and it is slightly excavated at that part of its 

 wall which, when the antennae are directed straight for- 



* Immediately beneath each of the eyes is a conspicuous black and 

 rounded ocellus-like elevation, which may represent the simple eyes of 

 PerijjaUis ; they are clearly not identical with the fenestras of Blatta, 

 which are, perhaps, the scai's of the lost antennules. It seems to me doubtful 

 whether the antennas of Blatta and Macliilis homologize with those of 

 Glomeris, in which, while the antennas occupy the place of the fenestras, a pair 

 of horse-shoe shaped membranous depressions, sinij;ularly like the anteunary 

 fossas of a cockroach, is in the position of the antcnn;\! in Blatta. 



•f- For the benefit of any one who may wish to obtain specimens of this 

 primitive form of insect for dissection, I may state that the species 

 abounded at the end of April and the beginning of May, 1878, on the 

 huge fallen blocks of Corallian rock that thickly strew the beach under 

 the ruins of Sandsfoot Castle, and on the slabs of stone from the Cornbrash 

 cliffs of the backwater, near Weymouth. All these ancient forms have a 

 remarkably wide distril)Ution. 



TRANS. ENT. SOC. 1879. — PART II. (jULY.) L 2 



