Miscellaneous. 155 



at which the author has arrived we think we cannot do better than 

 translate the most essential part of the summary which terminates 

 his memoir. 



" In all the insects observed, the body is composed of thirteen 

 segments behind the head. Nevertheless this number presents in 

 the Hymenoptera an apparent reduction, arising from the invagina- 

 tion of the last segment ; while in the Locustce. there seems to exist, 

 on the contrary, one segment more than usual, because, in the course 

 of development, the last segment divides into two parts — namely, a 

 posterior anal piece and an anterior annular piece *. 



" Both the sting and the ovipositor are formed of six principal 

 parts, of which, however, the number is reduced to five in the Hy- 

 menoptera which the auther has been able to observe, in consequence 

 of the soldering together of two of them. These six parts originate 

 from six papilla?, four of which belong to the penultimate segment 

 (12th behind the head) and two to the antepenultimate. These 

 papillae originate from disks (Imagindlsckeiben) similar to those 

 which Weissmann has described in connexion with the formation of 

 the appendages of Corethra ; but while in the Hymenoptera observed 

 these disks originate from an invagination of the hypoderm, which 

 thrusts itself into the cavity of the body in the shape of hollow 

 demispheres, we can recognize in Locusta only a thickening and 

 projection of the hypoderm exteriorly. The time of the appearance 

 of the six papilla? is not the same in all cases : in the bees, at the 

 commencement of the larval period the two papillae of the antepe- 

 nultimate segment and the two intermediate ones of the penultimate 

 appear simultaneously, while the two lateral papilla? of the latter 

 do not show themselves until later ; on the other hand, in the 

 grasshoppers, while still in the egg the two lateral papilla? of the 

 penultimate segment are already very much advanced in develop- 

 ment, the two of the antepenultimate segment are indicated in the 

 form of disks ; and the two intermediate ones of the penultimate 

 segment appear only when the animal has quitted the egg for some 

 time. We consequently see here, as in other cases of the develop- 

 ment of the Articulata, that homologous parts do not always appear 

 in the same order, but show themselves sooner or later according to 

 the dimensions which they have to acquire or the importance which 

 they will have in the sequel. 



" In the Hymenoptera observed, the sheaths result from the deve- 

 lopment of the two lateral papilla? of the penultimate segment, the 



* M. H. de Saussure,who has carefully studied the abdomeu of the adult 

 Orthoptera, has only found nine segments in these latter insects, besides 

 the intermediate segment, which has no ventral arch and belongs rather 

 to the thorax than to the abdomen. The body, therefore, would possess, 

 according to him, thirteen segments without counting the head (see 

 ' Memoires pom servir a THistoire Naturelle du Mexique &c.,' tome i. 

 p. 263, and ' Mission scientifique an Mexique &c./ Orthopteres, p. 2, pi. i.). 

 In the Hymenoptera the intermediate segment closes the thorax behind, 

 and forms that which has been wrongly called the metathorax. It is 

 then entirely separated from the thorax. 



