302 ITevr J. Wagner on the 



tubes. Yet if we start from von Kennel's assumption that 

 with the lengthening of the proctoda?um " even one or several 

 entire segments are invaginated together with the rudiments 

 of all the organs belonging to them," we may assume with 

 precisely the same justification that other glands also that 

 discharged their secretion through orifices in the integument 

 might be invaginated besides the nephridia. Moreover, it 

 must further be pointed out that in the Aphida3, which possess 

 no Malpighian tubes, the function of these organs is dis- 

 charged by the entire surface of the end-gut (Kowalewsky) ; 

 consequently we cannot found our conclusions upon func- 

 tional resemblance alone. It is also necessary to remark that 

 von Kennel bases all his assertions eitlier exclusively or 

 chiefly upon the study and the analysis of the organization of 

 Peripatus and the Myriopods, whereby he sometimes entirely 

 overlooks tlie peculiarities of the Arachnids. The fact that 

 the ]\Ialpigliian tubes of Hexapods and Myriopods develop 

 solely from the ectoderm, which is an important and univer- 

 sally recognized argument against the assumption that those 

 structures are homologous with segmental organs, remains 

 unrefuted. So long as it is not proved that the Malpighian 

 tubes, though it be only in part, are developed from the 

 mesoderm, I venture to side with the view that they arise 

 only through secondary local differentiation of the walls of 

 the end-gut j as is well known, this view is supported by the 

 fact that certain Copepods possess the faculty of excreting 

 uric acid compounds by the walls of their end-gut, as the 

 process also takes place in the Malpighian tubes of Insects ^. 

 Von Kennel's treatise led to the publication of the paper by 

 Zograff (No. 72), wherein the latter in general entirely 

 endorses the views of the former, though he deals chiefly with 

 the relations of the Arthropods to the Annelids, and does 

 not touch upon the question of the phylogeny of the various 

 classes of the Tracheata at all, since this is a problem " that 

 is so ably discussed and almost solved (?) by Prof, von 

 Kennel " {loc. cit. p. 294). From this it may be concluded 

 that the author has somewhat modified the view expressed by 

 him in his earlier paper on the development of the Myriopods 

 (No. 71, pp. 70 and 71), though he still continues to be in 

 favour of the theory of the common origin of the whole of the 

 Tracheata. Considering that in his first paper the autlior 

 writes, " the great similarity between the embryonic develop- 

 ment of the Myriopods and that of the Arachnids, which is 

 even greater than the resemblance between that of the former 



* Cf. p. 2!)6 siiprct. 



