T II E A N N A L S 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 



" perlitora spargite muscutn, 



Naiades, et circdm vitreos considite foiitcs : 

 Pollicc virginco tencros h'lC carpite florcs ; 

 Floribus et pictum, diva;, replete canistrum. 

 At vos, o Nymphse Craterides, ite sub undas ; 

 Ite, recurvato variata corallia triinco 

 \'ellite muscosis e rupibus, et mihi conchas 

 Ferte, Dese pelagi, et pingui conchylia succo." 



N.Parthcnii Gianneltasii Ed, 1. 



No. 25. JANUARY 1860. 



I. — OhsPTVations on iho. Distrihntion and Habits of the Pelagic 

 and Freshwater Free-jioating Diatomacefv. By Surgeon G. C. 

 Wallicu, M.D., llctived List, H.M. Indian Forces. 



1 HERE are three important points connected ^vith the natural 

 history of the Diatomaccaj upon which the information hitlicrto 

 recorded appears both scanty and unsatisfactory. These are — 



The laws whereby the bathymctrical range of these organisms, 

 in their hving state, is determined; 



The conditions under which their silicious remains arc depo- 

 sited and form vast sedimentary strata ; 



And, lastly, the extent and nature of their locomotive powers. 



In the * Synopsis of British Diatomaccre ' (vol. i. Introd. 

 p. xiii.) their distribution and habits are thus described : — 



" Their living masses present themselves as coloured fringes 

 attached to larger plants, or forming a covering to stones or 

 rocks in cushion-like tufts, or spread over the surface as delicate 

 velvet, or depositing themselves in a filmy stratum on the sand, 

 or intermixed with the scum of living or decayed vegetation 

 floating on the surface of the water. Their presence may be 

 often detected, without the aid of the microscope, by the absence, 

 in many species, of the fibrous tenacity which distinguishes other 

 plants; and when removed from their natural position, they 



Ann. ^- Mag. N. Hist. Scr. 3. Vol v. 1 



