Prof. E. R. Lankcster's Ilejoindcr to Prof. Chms. 181 



appearance which he gives to the two trees. If we leave the 

 word " Insecta " without a query on the left-hand branch of 

 my tree and strike the word out from the other branches of 

 the tree, and if we make the two main stems of the tree drawn 

 by Claus converge to their common base (as they must do and 

 are arbitrarily made not to do by Claus, thus producing an 

 illusory appearance of dissimilarity), the identity of Claus's 

 tree with that previously published by me is clear enough. 



6. Prof. Claus erroneously states (p. 62) that I have supposed 

 a new mouth to have formed in the Arthropoda as compared 

 with the Chfetopoda. I have made no such assumption. The 

 " adaptational shifting of the oral aperture " in relation to 

 the anterior appendages is, it would scarcely seem necessary 

 to point out, precisely the same thing as the " secondary shift- 

 ing " of the anterior appendages in relation to the mouth. 

 Yet it is with such a quibble as the assertion that these two 

 phrases describe different processes that Prof. Claus is anxious 

 to defend himself from the charge I have made against him 

 of a want of fairness in the treatment of his predecessors' 

 views as to the homologies and classification of the Arthro- 

 poda ! 



Prof. Claus further has given expression to the remarkable 

 conception that he is justified in ignoring the work of other 

 zoologists, and treating their results as his own, provided that 

 he does so not more than three years after they have published 

 those results. He quotes (p. 63) his work on the Daphnidae 

 of 1876, as containing the doctrine of an upward movement 

 of the postoral appendages which was, he admits, published 

 by me in 1873 ; and he wishes the reader to regard this as a 

 justification for his completely abstaining from referring to my 

 publication either in 1876 or in any of his subsequent writings. 



Is it possible to believe that Claus really considers that 

 the fact that he published a certain view in 1876 justifies him 

 in abstaining from all reference to an author who published 

 three years previously the same view ? 



I am of opinion that it was necessary (however unplea- 

 sant) to point out emphatically the unfair treatment to which 

 my writings in reference to the Arthropoda have been sub- 

 jected by Prof. Claus. I felt the more impelled to undertake 

 this unpleasant duty because it is witliin the knowledge of 

 those who have studied Seison, the parasitic Isopoda, and the 

 Daphnidse, that Prof. Claus is accustomed to escape with 

 insufficient criticism from the results of his peculiar forget- 

 fuluess. 



I by no means hold that a copious and original observer 

 like Prof. Claus is bound to discuss or to oive references to 



