1897. A^E THE ARTHROPODA A NATURAL GROUP? 103, 



I THANK you for your letter with the enclosed communication by 

 Professor Hutton. But it is impossible for me, in only a few days, 

 to work out so good an answer as I could wish, besides, for the 

 present I am much engaged with other work. 



During more than ten years I have spent much time preparing a 

 paper on the structure and morphology of the skeleton, etc., in all 

 orders of Crustacea and Myriopoda, and some orders of Insecta. A 

 kind of preliminary note has been' published in the Zoologischer 

 Anzeiger for 1893 (translated in Ann. S^ ^(^g- Nat. Hist., 6 ser., vol. 

 xii., pp. 417-34), and I hope that the final paper will be published in 

 a few years. Before this publication I do not wish to enter into any 

 further discussion on this subject, as I believe it will be better to be 

 able to refer readers to the full representation of the numerous details 

 in the said work. 



In this short answer I cannot make use of the modern termino- 

 logy, since I dislike ancestor-hunting and pedigrees. It seems to me 

 that too many authors take special pleasure in the construction of 

 new " trees," and I must confess that I am not able to recognise the 



Fig. I. — Mandibles with their Muscles seen from Below. 



A. Diastylis goodsiri, Bell. B. Japyx solifugus, Hal. (after Meinert, 1S65). 

 C. Blatta [Periplaneta) Americana, Fabr. 



utility of these interesting forests. As to the Arthropoda, new facts, 

 thorough-going studies of the adult animals are exceedingly wanted ; 

 further speculations on the facts at present generally known will, in 

 my opinion, be of no value. 



And now some remarks on the question itself. The lower mala- 

 costracous Crustacea and the Thysanura are, in my opinion, more 

 closely related to each other than hitherto recognised. Here I shall 

 produce but some few facts. If good figures of the mandibles with 

 their muscles of Nebalia, Diastylis (belonging to the Cumacea) and 

 Blatta, as types for lower Malacostraca and for the Orthoptera, were 

 laid before a zoologist, and then figures of the same parts of two 

 Thysanura, such as Machilis and Japyx, were shown him without 

 telling him the names of these two animals, he would say without 

 hesitation that the mandibles of the Thysanura belonged to Crustacea, 

 and not at all to Insecta. The three accompanying figures (Fig. i) 

 will, I hope, illustrate this statement, and the following explanation 

 will be satisfactory for this purpose. In Diastylis and Japyx we find 



