212 



SCIENCE- G OS SIP. 



deteriorate in its performance when used with a 

 high-power ocular to gain the needed magnifica- 

 tion. 



C. Baker's New Catalogue. — Mr. Charles 

 Baker has sent us his latest catalogue, which is an 

 enlargement and revision of the previous issue. 

 The arrangement of the contents might with ad- 

 vantage be copied by other makers. The first 

 division contains particulars of microscopes, illu- 

 minating apparatus, mechanical accessories, and 

 apparatus for recording observations, all in due 

 order. The succeeding divisions are devoted to 

 apparatus for collecting, preparing, mounting, and 

 storing specimens ; to apparatus for bacteriology, 

 blood examinations, and medical analysis ; and to 

 lists of microscopic slides, models, and specimens. 

 Notable features are the explanations and excep- 

 tional detail as to measurements in regard to each 

 entry in the catalogue. The very full list of objec- 

 tives includes those of Leitz, Reichert, and Zeiss, 

 as well as Mr. Baker's own series, and is very con- 

 venient for reference. We observe, however, some 

 errors in the calculation of total magnifications 

 with eyepieces of stated powers with a tube-length 

 of 160 mm. The well-arranged list of stains, 

 mainly from the laboratory of Dr. G. Grubler, of 

 Leipzig, will be of service to all microscopists, the 

 list of mounting sundries being equally complete. 

 The pages devoted to mounted objects are con- 

 siderably extended, especially as regards the slide- 

 lending department {ante, pp. 153, 154), and we 

 note that the prices of individual slides have been 

 largely revised, in accordance, we understand, 

 with a suggestion made in these pages when the 

 previous edition of the catalogue was noticed. 



ANSWERS TO CORRESPONDENTS. 



F. A. H. (Epsom). — The particulars you give are 

 scarcely explicit enough to enable me to help you. 

 Can you give me an exact drawing — or, better still, 

 send the slide itself, that I may be sure to what it 

 is you allude. 



[For further articles in this number on Micro- 

 scopical subjects, see pp. 197 and 200.] 



MEETINGS OF MICROSCOPICAL SOCIETIES. 



Royal Microscopical Society. — 20 Hanover 

 Square, December 18th, 8 p.m. 



Quekett Microscopical Club. — 20 Hanover 

 Square, December 6th, 7 p.m. ; December 20th, 

 8 p.m. 



Manchester Microscopical Society. — Grand 

 Hotel, Manchester, December 5th, 7 p.m. ; Mount- 

 ing Section, December 19th, 7 p.m. 



Sunderland Microscopical Society. — Sub- 

 scription Library, Sunderland. December 17th, 

 7.30 p.m. 



EXTRACTS FROM POSTAL MICROSCOPICAL 

 SOCIETY'S NOTEBOOKS. 



[Beyond necessary editorial revision these ex- 

 tracts are printed as written by the various 

 members. — Ed. Microscopy, S.-G.] 



Fossil Polyzoa.— Figs. 1, 2, 3, and 4 represent 

 fossil Polyzoa from the Wenlock beds of the Upper 

 Silurian. Figs. 5, 6, 7, 8, and 9 represent fossil 

 Polyzoa from the Coal Shales (Scotland) of the 

 Carboniferous period. Allman's definition of 

 Polyzoa is as follows: — '•Alimentary canal sus- 



pended in a double-walled sac, from which it may 

 be partially protruded by a process of evagination, 

 and into which it may be again retracted by 

 invagination. Mantle surrounded by a crescent of 

 hollow ciliated tentacles. Animals always forming- 

 composite colonies." These polyzoa live in colonies 

 or " polyzoaria." Each polyzoarium consists of an 

 assemblage of distinct but similar zooids arising 

 by continuous gemmation from a single primordial 

 individual. They possess sexual organs and are 

 hermaphroditic. Polyzoa belong to a very ancient 

 race. They seem to have been present in great 

 numbers both in Silurian and Carboniferous beds. 

 Though one branch of the family, the Fenestella or 

 " Lace Corals," appears to have died out with 

 the Carboniferous period, representatives of this 

 large as well as ancient family have existed in 

 more or less abundance throughout a great portion 

 of the Primary, Secondary, and Tertiary Periods, 

 and are, as we know, to be found in many parts of 

 the world at the present time. I have in my pos- 

 session upwards of sixty fossil species extending 

 over the four great geological periods. The fact 

 that this family has existed so long and varied, 



"H,r^ 



Fossil Polyzoa. 



comparatively speaking, so little, shows, to my 

 mind, how well it has been suited from the first to 

 its environment, and how well it has been able to 

 hold its own in the struggle for existence, whilst 

 many of its contemporaries in each of the four 

 great geological periods have become extinct. It 

 may be, however, that the environments have not 

 differed sufficiently to produce any great change, 

 or that the organism is not sufficiently sensitive to 

 such change. See Darwin's " Origin of Species." 



(To be continued.) 



