July 7, 1923] 



NA TURE 



ities of the somatic cells are curtailed by some special 

 cytological mechanism, which, be it marked, has not 

 hitherto been described by any one in the Vertebrata. 



The nearest approach to such a mechanism is the 

 chromatin-diminution process in Miastor, an insect 

 in which all but the germ cell nuclei are deprived of 

 part of their chromatin. Nowadays, however, few 

 zoologists wish to repeat the mistake of Weismann in 

 deducing too much from the peculiar cytology of the 

 holometabolous Hexapoda, which develop under 

 special conditions. J. Bronte Gatenby. 



Trinity College, Dublin, 

 June 9. 



Origin of certain Filamentous Forms 

 from Eocene Beds. 



A PAPER by Prof. T. D. A. Cockerell has just 

 appeared entitled " The Supposed Plumage of the 

 Eocene Bird Diatryma " [Amev. Mus. Novitates, No. 

 62, 1923), describing certain filamentous bodies from 

 Eocene (Green River) beds of Colorado. 



Prof. Cockerell states that the specimens " are not 

 vegetable fibres, nor are they mammalian hairs," but 

 resemble the simple feathers of birds like the casso- 

 wary, and he refers them (with a query) to a new 

 species of Diatryma because this is the only known 

 Eocene bird from which they could have come. 



Prof. Cockerell has been good enough to give the 

 original of his Fig. iB to the Geological Department 

 of the British Museum (Natural History), and an 

 examination of this specimen has failed to convince 

 me that it is not of vegetable origin. Similar strands 

 of filaments occur in Upper Eocene rocks of Haering, 

 Tyrol, for example, and are derived from decayed 

 leaves of palms {Sabal major, Ung.), into undecayed 

 portions of which they are sometimes seen to pass. 

 These fibres in specimens from Haering are absolutely 

 indistinguishable from those in the original of Prof. 

 Cockerell's Fig. iB, and, though it is difficult to arrive 

 at any definite conclusion from such fragmentary 

 material, it seems quite possible that the supposed 

 feathers may be only fibres from a decayed mono- 

 cotyledonous leaf. W. N. Edwards. 



Geological Dept., 



British Museum (Natural History), S.W.7, 

 May 26. 



Hafnium and Geltium. 



It is with great interest that I have read the 

 communications of Dr. Coster and Prof. Hevesy in 

 Nature on the new element, hafnium. Under the 

 title " Correlation of Atomic Structure and Spectra " 

 (Journal American Chemical Society, xliv., p. 328, 

 1922) I discussed the properties of the unknown 

 elements from the point of view of Bury's theory of 

 atomic structure, and stated : " No. 72 possibly is 

 Urbain's celtium. But Bury's arrangement gives 

 the electron structure 2. 8. 18. 32. 8. 4 for this element, 

 which is consequently tetravalent, while Urbain 

 describes celtium as being intermediate in chemical 

 character between Lu and Sc, both trivalent elements. 

 A further investigation of the chemical properties 

 and the X-ray spectrum of celtium is therefore 

 desirable." This article was received by the editors 

 of the Journal, November 22, 192 1, and, I believe, is 

 the first published suggestion that the chemical 

 properties of celtium as given by Urbain do not agree 

 with theoretical considerations of atomic structure. 



Harold S. King. 



The Chemical Laboratory, Dalhousie University, 

 Halifax, Nova Scotia, May 12. 



NO. 2801, VOL. I 12] 



Distribution of Limnsea pereger and L. truncatula. 



Some recent observations on a subject lately dis- 

 cussed in the columns of Nature may be of interest. 



The freshwater snails, Limncea pereger and L. 

 truncatula are widely distributed over this district, 

 where Distomuni hepaticu^n is a serious pest : the two 

 molluscan species occur in almost every body of 

 fresh water where the topographical conditions are 

 suitable, excepting only such as are seriously pol- 

 luted by the effluents from old lead-workings. The 

 hydrogen ion concentration of the fresh waters varies 

 generally from about Ph 6-4 to Ph 6-9. 



While studying a neighbouring area, a portion of 

 the Plynlimmon plateau, about 12 to 15 miles from 

 Aberystwyth, I was struck by the almost complete 

 absence of freshwater molluscan species. Two only 

 were found : L. pereger and Ancylus fluviatilis, the 

 latter in a single locality only, the former in this and 

 one other locality. The hydrogen ion concentrations 

 of the waters in these two localities were Ph 6-4 and 

 . Ph 6-5 respectively : both are exceptional figures for 

 the area, where the Ph values as a rule range from 5-8 

 to 6-2. (Peat bogs abound in the district.) 



Laboratory experiments show that L. pereger 

 invariably dies within 2 to 3 hours after being placed 

 in water of Ph value 5-6. (Distilled water which had 

 been exposed to the air was used for these experi- 

 ments ; also tap water, which has here about the same 

 Ph value.) A characteristic reaction is given, the first 

 phase of which is the nearly complete extension of the 

 body beyond the shell, with violent twisting move- 

 ments. Eventually the animal dies in retraction, 

 with much exudation and coagulation of mucus. I 

 intend before long to carry out similar experiments 

 with L. truncatula. Several other freshwater species 

 show a similar reaction, the coagulation of the mucus 

 being especially noticeable. 



Kathleen E. Carpenter. 

 Zoological Department, 



University College of Wales, 

 Aberystwyth. 



Scientific Names of Greek Derivation. 



In the course of the interesting notice of Stille's 

 " Die Schrumpfung der Erde " in Nature of June 2, 

 reference is made to "What G. K. Gilbert styled 

 ' epeirogenic ' (now written ' epirogenetic ')." The 

 latter termination is no doubt more correct, but the 

 spelling of the second syllable involves a more debat- 

 able question. Some of us are by no means reconciled 

 to the system of the Latinisation of Greek names, now 

 widely followed, especially on the other side of the 

 Atlantic. It is a distinct misfortune that Greek 

 should reach the nomenclature of science by way of 

 a language poorer in both vowel and consonantal 

 sounds. To write " dinosaur " for " deinosaur " is 

 to obscure the derivation of the word. So long as 

 most of our scientific terms are derived from Greek, 

 it is obviously desirable that they should be written 

 in English in a form as closely similar as possible to 

 the original, so that a student can look them up in a 

 lexicon even if he knows but little more of the 

 language than the letters. 



I am glad, however, to see that your reviewer, 

 when he is at liberty to follow his own predilections, 

 prefers to adhere as far as he can to the Greek 

 spelling. Does he not speak of " Okeanos, lord of 

 the great outer seas " ? John W. Evans. 



Imperial College of Science and Technology, 

 S.W.y, June 4. 



