360 



CORRESPONDENCE. 



Hydrachna globula (Duges). 



In brea vjng up a specimen of Dytiscus marginalis, which had been in spirit for 

 some months ( I found a nymph of Hydrachna globula (Duges) imbedded in the fat- 

 body on the left side, near the first abdominal spiracle. Since then I have learned 

 that Mr. G. E. Mainland, F.R.M.S., had a similar experience some years ago. 

 Dr. Trouessart has kindly identified the specimen for me, but he offers no suggestion 

 as to how the mite — common enough as an external parasite on Dytiscus, Nepa, and 

 Notonecta— got into such strange quarters. I shall be grateful for help on this point. 

 The specimen is now at the British Museum (Nat. Hist.) in the care of Mr. Pocock. 



9 Cavendish Road, Harringay, N. Henry Scherren. 



A Council of Zoologists. 



Your proposal with reference to the Nomenclature question is an interesting 

 one. If it be possible for the German Zoological Society to publish a synopsis of 

 the Animal Kingdom, it certainly should be possible for the names of extinct species 

 to be added to it. Assuming the truth of Dr. Sharp's estimate as to the number of 

 recent species (and almost the same estimate has been made independently and 

 synchronously by an American systematist), we need not suppose that it would be so 

 very greatly increased by the addition of extinct species. It is the Insecta that swell 

 the numbers of recent species, but their fossil representatives are very few. Perhaps 

 a series of Palseontological Appendices. to the various parts of "Das Tierreich " 

 might be arranged. But you are right in urging the prior completion of a list such 

 as Mr. Sherborn's " Index Specierum." X, 



When the Council which you suggest has been appointed, it might draw*up an 

 "Index Expurgatorius " of publications. There are writers who, without o -ubt, 

 should not be treated as serious workers, and who would be blackballed by all 

 true zoologists. Recorder. 



Some Corrections. 

 Mr. Theodore Groom asks us to state that in his letter in our April number 

 on p. 287 the words "long cylindrical glass troughs" should be "long rectangular 

 glass troughs." In the third paragraph of Mr. Pycraft's article on "The Wing of 

 Archasopteryx," p. 261, the implication that Dr. Hurst regarded the bone that he 

 provisionally named (not identified as) " ulnare," as belonging to the proximal row of 

 carpals, is contrary to fact. It was also incorrect to state that Owen figured it as 

 the radiale. 



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The " Challenger " Number. — In reply to enquiries, we remind our 

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