Io8 NATURAL SCIENCE. February. 



by the structure of the limbs, especially of the jaws, and of the 

 tracheae, and with the latter by the slight development of the limbs. 

 It was merely a freak of nature, that the conditions which influenced 

 the formation of the body of Peripatiis were different from those that 

 affected other arthropods. After careful consideration of the com- 

 parative anatomy and ontogeny of these animals, the type 

 " Arthropod " appears to me, if we omit their primitive ancestors, 

 not sufficiently comprehensive, and I recognise the advisability of 

 accepting Cuvier's type Articulata, divided into Arthropoda and 

 Annelida, all the more since this type could, by means of the 

 Trochophore, be united with the Mollusca in a common genealogical 

 tree. 



A. Jaworowski.^ 

 Lemberg. 



The questions raised by Captain Hutton should have more space 

 for their adequate discussion than Natural Science can afford. I 

 will therefore give my views upon the subject in outline only, and 

 would refer the reader for more details and for a tolerable bibliography 

 to my paper on the Classification of the Arthropoda [American 

 Naturalist, vol. xxviii., 1894, Tuft's College Studies, No. i). Some 

 thirteen years ago [Avier. Nat,, vol. xvii., 1883) I was troubled with 

 almost the same questions as those bothering my antipodean 

 colleague, and now, although my line of argument would be much 

 different from that then adopted, my views are essentially unchanged. 

 It is interesting to note that von Kennel, in his "Lehrbuch der 

 Zoologie " (1893) ^^d ^^ other papers, has adopted similar views. His 

 researches upon Peripatiis entitle his opinions to consideration. 



The first question, that in regard to the importance of the 

 nauplius, can be briefly answered. I think that most morphologists 

 at present regard it as an adaptive condition introduced early in the 

 phylum and not as representing an ancestral condition. Any other 

 view leads to inextricable difficulties. The nauplius, I think, can 

 safely be ignored in any discussion of the inter-relationships of the 

 Arthropoda. 



Next comes the question concerning Peripatns. Has it that 

 importance in phylogeny which it seemed it must have when 

 Moseley's investigations were first published ? Is it an arthropod ? 

 Is it an annelid ? Or is it a representative of a distinct group ? As 

 my views upon these points are somewhat at variance with those 

 held by many morphologists, I may be permitted to say a few words 

 concerning them. 



Peripatus differs from all arthropods in several features. It has 

 functional nephridia, repeated metamerically in most of the segments 

 of the body ; while so far as I am aware no true arthropod has more 

 than two of these organs. Striped muscle is found nowhere in 



1 Kindly translated from the German by Mrs. H. M. Bernard. 



