440 M. N. Cholodkowsky on the 



afresh through new adaptation from a rudimentary or even 

 latent condition, and thus new conditions of organization 

 arise whicli, with equal justice, may be regarded as either 

 primitive or secondary." I give this quotation here in order 

 to point out that some years ago I already drew attention to 

 the possible (and probable) great importance of atavism in 

 ontogeny and phylogeny * by designating the cases of this 

 class as " normal periodic atavism." While T thus agree 

 with Herr Emery in considering it, as a matter of principle, 

 a very probable possibility that organs which are secondary 

 in ontogeny may be homologous with those which are primaiy 

 in phylogeny, I nevertheless regard it as superfluous, and 

 even impossible, to apply this view to caterpillars. That 

 the polypod caterpillars cannot be derived from hexapod 

 {Camjwdea-Yxk^) larvre is proved at once by the fact that tiie 

 latter may themselves be polypod in their embryonic deve- 

 lopment (e. g. HycIro]}hilus). The entire difference between 

 hexapod and polypod Insect larvae thus depends upon the 

 circumstance that in the former the abdominal legs atrophy 

 before the animal is hatched, while in the latter they persist 

 in post-embryonic development. It is clear from the embryo- 

 logy of Insects that the polypod larvaj cannot be derived from 

 the hexapod ; on the other hand, however, paleontology 

 teaches us that the oldest Insects possessed an incomplete 

 metamorphosis, and therefore were hexapod after leaving the 

 Qgg, and that consequently also the hexapod larvas are not to 

 be derived from polypod forms. Thus the only alternative 

 is to suppose, what is also most natural, that the hexapod as 

 well as the polypod larvae in different orders of Insects have 

 arisen independently of one another. 



Having discussed the question of the abdominal extre- 

 mities of caterpillars, I must also briefly allude to the abdo- 

 minal appendages of the other Insect larvae. As I have 

 stated above. Dr. Haase has gathered together in his new paperf 

 almost all the instances which belong to this category. Un- 

 fortunately he at the same time utilizes for his deductions 

 almost exclusively zoographical and anatomical facts, while 

 on the other hand he appears to regard the results of compa- 

 rative embryology as superfluous. Thus, for instance, it is 

 enough for him to establish the fact that the abdominal 

 appendages do not lie directly in prolongation of the line of 



• Cholodkowsky, " Sur la morphologie de I'appareil urinaire des 

 L^pidopteres," Arckives de Biologie, t. vi., 1885, pp 497-514, pi. xvii. ; 

 *' Sur les vaisseaux malpigbieus des L^pidopteres," Coinptes Rendus 

 Acad. Paris, t. xcviii. pp. 6.31-633, t. xcix. pp. 816-819 (1884). 



t Op. cit. 



