HARD VVICKE'S «C I EK CE-G OS SIP. 



207 



MICROSCOPY. 



A FiNBER FOR HaRTXACk's MICROSCOPES.— 



Those of our readers who use Hartnack's, or micro- 

 scopes of similar construction, will find Mr. Hicks's 

 contrivance for the purpose of easily refinding an 

 object at any time very useful. A line is to be 

 ruled across the centre of the stage from side to 

 side. Crossing this line at right angles are ruled 

 two lines about two inches apart, one on either side 

 of the aperture of the stage. In order to use the 

 finder, a label about half an inch in diameter is fixed 

 to each end of the slide, the lines on the stage 

 left uncovered being used as guides for continuing 

 the lines across the label with a pencil-mark. If 

 the lines marked on the label be made to coincide 

 with those on the stage, the object on the slide will 

 be found in the centre of the field. Mr. Hicks says 

 that he finds roughing the ends of the slide with a 

 corundum file, and marking the point of intersection 

 with an ink dot, preferable to the labels, as being 

 more accurate. We think a label somewhat less 

 than an inch square (about nine-tenths of an inch), 

 so as the stage lines might be seen round the mar- 

 gins, would be more advantageous than those of a 

 circular form, as the position of the stage-lines 

 could be marked on the margin of the label, ai:d the 

 position of the object might be registered by mar - 

 ing down the number of dots from the top left-hand 

 corner ; supposing it to be the fourth in a vertical 

 and the seventh in a horizontal direction, it could 

 be registered either 4 | 7— or i.—K. 



MiCROGRAPHic Dictionary.— The third edition 

 of this magnificent work has now reached the four- 

 teenth part, and is about halfway through its 

 course. The delay in its publication may be par- 

 tially attributed to the little leisure left to its 

 editors, as well as to the fact that the newest 

 information relating to microscopical research lias 

 been incorporated. The editors are Dr. J. W. 

 Griffiths, Professor Martin Duncan, Professor Hu- 

 pert Jones, and the Rev. M. J. Berkeley. To the 

 young microscopist this work will prove a vade- 

 mecum, and to the microscopical amateur it offers 

 itself as a repertory of microscopical knowledge, 

 easily attainable, and thoroughly trustworthy. The 

 publisher is Van Voorst, 1, Paternoster-row, Lou- 

 don, 



Organisms IN Chert.— The remains offoramini- 

 fera, prisms from shells of Inoceremas or Pinna, 

 small moilusca, and fragments of bryozoa, are not 

 uncommon either in chert or flint nodules. All 

 these remains represent the internal rather than the 

 external form of the shell. As it is not very apparent 

 why this should be the case, the following theory 

 will perhaps explain it. All the specimens I have 

 had an opportunity of studying, when examined as 



opaque objects, are either of a chalky whiteness or 

 coloured with peroxide of iron; in this condition 

 the siliciQed casts of foraminifera and other organ- 

 isms are found in recent dredgings. In a highly 

 interesting dredging made by Captain Perry, off Navy 

 Bay, Colon, Panama, silicified casts of foraminifera, 

 small moilusca, borings of some species of cliona, 

 fragments of bryozoa, and species of echinus, occur 

 in considerable quantities. It therefore seems pro- 

 bable that these remains occurring in the chert and 

 flint nodules were silicified before they became em- 

 bedded in the flint. The little spiral organism 

 figured in the August number is certainly not that 

 of foraminifera, but some small mollusk, the two 

 lower figures representing transverse sections of the 

 same or a similar form. — F. K. 



Chloride of Barium as a Preservative. — 

 This salt, \i hich we recommend for use in glycerine 

 jelly, and which may prove a useful preservative for 

 oiher mounting media, &c., is seldom kept by 

 druggists, and has to be procured from the scientific 

 chemist. It is sold (price 2d. per oz., or by post 

 3id.) by Towuson & Mercer, 89, Bishopsgate-street 

 Within.— IT. M. J. U. and F. J. A. 



Origin of the Red Blood-Corpuscles. — As to 

 the origin of these corpuscles invertebrates, the fact, 

 as stated in Science-Gossip, August, 1874, page 183, 

 has long been so well known in England that no 

 further corroboration of it was needed from abroad. 

 Yet we see it widely published, as if Dr. H. D. 

 Schmidt, from the result of his own investigations, 

 has very recently discovered that "the nucleus only 

 of the colourless blood-corpuscles is developed into 

 the red corpuscle," which his pages might otherwise 

 countenance. The truth is that neither Dr. H. D. 

 Schmidt, nor any German, has or ever had any just 

 claim whatever to this important discovery. It is 

 due wholly to the researches of our countryman, 

 Mr. Wharton Jones, w hose original memoir on the 

 subject, entitled "The Blood-corpuscle considered 

 in its different Phases of Development in the Animal 

 Series," was published in the " Abstracts of Papers 

 communicated to the Royal Society of London," 

 June 19, 1843 ; and at length, with illustrations by 

 beautiful plates, in the next succeeding part of the 

 " Philosophical Transactions." Scarcely any physio- 

 logical contiibution is better known than this in 

 Britain ; for example, in Professor Gulliver's lec- 

 tures on the blood, delivered at the Royal College 

 of Surgeons, Mr. Jones's doctrine is discussed and 

 accepted, as may be seen by the reports of those 

 lectures in the Medical Times and Gazette for 18G2, 

 August 23, p. 188, and December 13, p. 623. That 

 " the spleen and lymphatic glands are the permanent 

 blood-formative organs," at least of the corpuscles 

 of that fluid, was the doctrine admirably supported 

 by William Hewson upwards of a century since, as 



