Morphology and PhyJogeny of Insects. 443 



embryonic development that further progress takes place. 

 According to Haase these appendages cannot be homologous 

 with the legs, because their earliest rudiments are purely 

 ectodermal. " This view," he writes, " which appears to 

 be supjiorted by Grassi also, was expressed for the first time 

 in 1872 by Uljanin, who demonstrated the development of 

 the gona})ophyses from subcutaneous imaginal disks." This 

 reference to Uljanin, which, as I shall immediately show, is 

 quite unjustifiable, is doubtless due to Dr. Haase's ignorance 

 of the Russian tongue ; for, contrary to what is stated by 

 Dr. Haase, Uljanin expresses his deep conviction that the 

 parts of the sting are homologous with the legs and that the 

 lancets correspond to one, and the quadrate plates together 

 with the sheath to another pair of legs. It is also proved by 

 Uljanin that the thoracic legs likewise develop from sub- 

 cutaneous imaginal disks, so that no difference really exists 

 between the mode of development of the thoracic legs and 

 that of the abdominal a})pendages. There is consequently no 

 reason for not regarding the bee's sting as homologous with 

 the thoracic legs. 



The embryology of the bee also furnishes excellent evidence 

 of the justice of the view which, as I have stated above, I 

 expressed years ago *, that organs also which are really 

 secondary in ontogeny may have just the same morphological 

 and phylogenetic value as undoubtedly primary structures. 

 The thoracic legs of the embryo of the bee are so strongly 

 developed that they have been observed by every one of the 

 embryologists who have investigated the development of the 

 animal in question. These legs diminish in size as the deve- 

 lopment of the embryo proceeds, and become transformed into 

 flat ectodermal disks (Kowalevsky). It is only in the course 

 of larval and pupal life that they undergo further develop- 

 ment and become definite legs. The thoracic legs of the bee 

 are therefore secondary according to their mode of develop- 

 ment ; yet it will scarcely occur to any one to doubt their 

 homology with the thoracic legs of other Insects. Just as 

 " secondary " are also the thoracic legs of the bark-beetles 

 (according to the investigations of Packard f, which I can 

 confirm from my own studies), of the flea (according to Bal- 



* Cholodkowsky, " Sur la morphologie de I'appareil urinaire des Lepi- 

 dopteres," Archives de Biologie, t. vi., 1885, pp. 407-514, pi. xvii. ; " Sur 

 les vaisseaux malpigbieus des Lt^pidopteres," Coniptes Keudus Acad. Paris, 

 t. xcviii. pp. 631-(j;J3, I. xcix. pp. 81G-81U (1884). 



t Packard, " The DevelopDient of the Bark-Beetles {Xylebonis and 

 I[i/lu>'(/ops)" U. S. Department of Agriculture, 3rd Eeport of the Euto- 

 molofrical Commission (AVashiugtou, 1883), pp. 280-282, pi. x.\ii. 



