Morphology and Phylogeny of Insects. 435 



two abdominal appendages, which are in every respect similar 

 to legs, so that their homology with the thoracic limbs is 

 hardly open to doubt. With regard to the ventral tube it is 

 supposed by Ilaase that this corresponds to the ''ventral 

 sacs " of jfachtlis, ScoJopendrella, Campodea, &c., wherein 

 he again disregards embryological facts ; for it was proved by 

 Uljanin that the ventral tube develops from two anterior 

 abdominal appendages, which are quite similar to, and almost 

 certainly homologous with, the thoracic legs, while the ventral 

 saccules, e. g. in Scolopendrella, occur on the same segments as 

 those on which limbs are also present, and therefore cannot 

 be homologous with the legs. With regard to the pyriform 

 appendages of the first abdominal segment of certain Insect 

 embryos Haase expresses himself very vaguely ; for while he 

 considers their homology with the ventral saccules to be also 

 somewhat doubtful, he nevertheless believes that they possess 

 a similar (respiratory) function, and that " it is probably a 

 latent ancestral character that allows these structures, which 

 are so entirely analogous to one another, to arise once more at 

 the same places." Embryology, however, shows most 

 distinctly that the pyriform appendages develop from typical 

 leg-like structures, indisputably homologous with the thoracic 

 limbs, and that therefore there can be no question of homology 

 witli the ventral saccules of Myriapods and Thysanura. As 

 to the function of the pyriform appendages, this is in all 

 probability the same as that of the ventral tube of the Podu- 

 rid^e, wliich, according to Haase, climb up glass by the help 

 of this organ (though they are also capable of doing so 

 without its assistance). That the pyriform organs are adhe- 

 sive was the conclusion previously arrived at by liathke *, 

 according to whom in extracting embryos of Gryllotcdpa from 

 the embryonic envelopes the " mushroom-shaped bodies " 

 are easily detached and remain sticking to the envelopes f. 

 The latest statements of Wheeler J, Graber§, and Nusbaum || 



Nachricliten d. Moskauer Gesellsch. d. Liebliaber von Naturwisseusch. 

 &c., 1875, Bd. 16, Lief. 3, pp. 1-10, Taf. iii.-v. (in Russian). 



* Ratlike, " Zur Eutwicklungsgeschichte der Mauhvurfsgrille," Arch, 

 f. Anat. u. Physiol. 1814, pp. 27-^8, Taf. ii. figs. 1-5, 



t Rathke was also the first to observe the facetted surface of these 

 appendages 



X W. M. Wheeler, " The Embryology of Blatta germanica and Dory- 

 phora decemlineata" Journal of Morphology, vol. iii. 1889, pp. 293-374, 

 pis. xv.-xx. 



§ Graber, " Ueber den Bau uud die phylogenetische Bedeutung der 

 embryonalen Bauchanhiinge der Insecten," Biol. Ceutralbl., Bd. ix. 1889- 

 1890, pp. 355-36;J. 



II J. Nusbaum, " Die Entwicklung der Keimblatter bei Meloe proscam- 

 hccus,'" Biol. Centralbl., viii., 1888, p. 449, 



30* 



