HARDWI CKE 'S SCIE NCE -GOS SIP. 



19 



When rinsed and dry the prints are permanent and 

 of a pleasing tone, and hardly distinguishable from 

 genuine copper-plate etchings. Any of the ordinary 

 photographic processes maybe adopted for printing. 

 For commercial work the glass etchings are far in 

 advance of any other method of producing photo- 

 lithograph and photo-relief blocks for letterpress 

 printing. 



Photo-Micrography. — I have tried photo-micro- 

 graphy as suggested by your correspondent, Mr. 

 Dean, in Science-Gossip for last February, and 

 have been most successful. Of course the principal 

 difficulty is in getting the right length of time for the 

 exposure, but one soon gets into the right way. — 

 P. Tracy, Ipswich. 



MICROSCOPY. 



The Royal Microscopical Society. — Rev. A. 

 Hall exhibited a bacillus from urine which closely 

 resembled B. tuberculosis. — Mr. Hardy exhibited and 

 described a little apparatus which he had devised for 

 the purpose of photographing an object under the 

 microscope without having to alter the position of 

 the instrument in any way. He had originally made 

 at in metal, but had found it too heavy ; the one now 

 before them was made of wood, and weighed about 

 one ounce, the cost being nothing at all beyond the 

 trouble of making it. — Mr. Watson exhibited and 

 described a new pattern microscope for students 

 {"The Edinburgh Student's Microscope") and a 

 student's petrological microscope made upon the same 

 lines ; also a small box for holding slides, for which 

 a patent had been obtained by Mr. Moseley, its 

 inventor. — Mr. Crisp exhibited apparatus by which 

 it was proposed to convert a microscope into a 

 microtome by placing the embedded substance in the 

 lower end of the tube, and cutting sections by means 

 of a blade fitted to move upon the stage plate. — Mr. 

 J. Mayall, jun., described the various microscopes 

 and accessories which he had examined at the Paris 

 Exhibition, pointing out that whereas at former 

 international exhibitions most of the best makers 

 in England, America, and other countries were 

 exhibitors, on this last occasion they had been rather 

 conspicuous by their absence. The French opticians 

 were fairly well represented as to numbers, but the 

 instruments they exhibited were, for the most part, 

 of the old, not to say antiquated, types. He had 

 seen very little that was new in the matter of design. 



A New Microscope. — Our contemporary ("Re- 

 search ") states that a new microscope has beeninvented 

 by Dr. E. Schulze, director of the Zoological Institute 

 at Berlin, and is called a " horizontal microscope. " It 

 rests on a perpendicular stand, and its chief feature is 

 an aquarium, which contains the object to be examined. 

 The aquarium is a cavity made of panes of glass, lit 



by reflected light from a movable mirror. The 

 cylinder of the microscope can be brought into three 

 different positions by means of screws, and moved in 

 all directions to enable an examination of every part 

 of the object. For watching small moving animals 

 this new instrument will be most useful. 



Embryonic Rotifers. — With reference to Dr. 

 Barnett Burn's query, in his article on Philodina 

 tuberculata (Science-Gossip, Dec.) as to the 

 position occupied by the embryo rotifer within the 

 parent, the following note made by me just a year ago 

 may be of interest in affording an answer. In a 

 Rotifer ("vulgaris," I believe) that I had under 

 observation during some three hours, and in which 

 a well-developed foetus was present, the position of 

 the latter relatively to its parent was several times 

 changed, the head of the embryo being, when first 

 noticed, in the same direction as that of the parent, 

 afterwards turned towards the opposite extremity of 

 the latter's body, again brought back to its original 

 position, and finally again reversed. The embryo was 

 large and perfectly formed, exhibiting well its two 

 eye-spots and the ciliary action within its pharynx, 

 and working its trophi intermittently. I think this 

 observation alone (though doubtless often confirmed 

 by others), will prove that the position of the foetus 

 in the viviparous Rotifera is not at all constant within 

 the adult, at any rate during the later stages of 

 development, and that this, therefore, can be of no use 

 whatever as a means of classification.— P. Thompson. 



The October number of the Journal of the Royal 

 Microscopical Society contains the following papers : 

 " Description of a New Species of Megalotrocha," by 

 Surgeon V. Gunson Thorpe, R.N. (illustrated) ; 

 " Note on Polarizing Apparatus for the Microscope," 

 by Professor S. P. Thompson, D.Sc, and also the 

 usual "Summary of Current Researches." 



ZOOLOGY. 



Cuckoo and Wagtail (misprinted Magpie in 

 last number of Science-Gossip).— J. A. Smith may 

 be assured that it is by no means infrequent for the 

 cuckoo to make use of wagtails and other birds as 

 foster-parents as well as hedge-sparrows. A few 

 years ago, walking round a friend's garden, near 

 Ross (Herefordshire), I noticed two unfledged birds 

 lying dead at the base of the wall. On looking 

 closer under the shade of a potato stalk, I dis- 

 covered the nest of a pied wagtail built a few inches 

 in the ground, in a cavity where a stone had fallen 

 out. In the nest was a robust young cuckoo, and at 

 a little distance one of the old wagtails waiting with 

 an insect in its bill ready to drop into the mouth of 

 the usurper, about whose welfare they were more 

 concerned than the fall of their own progeny de- 

 caying close to the comfortable home from which 



