SCIENCE- G OSSIF. 



333 



cells i- stated to be 2 to •"> m- and thai of the 

 families 60 /it and more. The alga is probably no1 

 rare; bul a- it was not recognised by two or three 

 microscopists to whom it was shown, it is mosl 

 likely M'Miim n.it ici-i 1, ami certainly does not com- 

 monly occur in such cumbers as to give any tint to 

 the water it inhabits. 



Attempts to mount these algae in several pre- 

 parations of glycerine were not successful, the 

 groups breaking up. Chlor-zinc-iodine (Schnlze's 

 solution) gave better results. So did some other 

 fluid media ; but the distinctive characteristics are 

 hardly likely to be enduring. 



A somewhat more remarkable instance, both as 

 to the colour and its cause, came under notice in 

 January, 189S, in a farm pond at Hampstead. 

 When first seen the water appeared of a rosy-pink 

 tint, owing to a growth which had formed on dead 

 leaves and debris of various kinds. About a week 

 later, however, the pond presented a striking as- 

 pect. When some distance from it, the water 

 seemed to be of a beautiful intense red-purple, so 

 exactly resembling what might be reflected from 

 the sky in a fine winter sunset that I involuntarily 

 turned round as I approached, almost expecting to 

 see the sun setting behind. On closer examination 

 it was seen that every leaf and twig at the bottom 

 was of this brilliant tint. Some floating patches 

 of Confervae looked like masses of vivid purple, 

 without a particle of their normal green being- 

 visible. The organisms producing this effect were 

 spread in a thin layer over everything, and also 

 formed delicate filaments lightly attached, which, 

 however, were dissipated by the slightest move- 

 ment. On agitating the Confervae or leaves, the 

 colour-containing matter was at once diffused 

 through the water. 



Under the microscope it was found to consist of 

 exceedingly minute bodies, so small that a definite 

 outline could scarcely be made out with a power of 

 500 diameters. These were surrounded by a thin 

 layer of mucilage, and mostly aggregated into 

 hollow spheres ; many were solitary, but some were 

 gathered in masses. The filaments it was almost 

 impossible to examine in then original form, but 

 they were composed of the same minute bodies 

 disposed more or less in line. A friend kindly 

 brought the matter under the notice of a professor 

 of botany, who at once identified the organism as 

 a bacterium now named Bcggiatoa rosco-pcrsicina. 

 He referred me to a paper by Dr. Lankester, pub- 

 lished in "The Quarterly Journal of Microscopical 

 Science" for 1873, N.S., vol. xiii. Dr. Lankester 

 there describes, under the name of Bacterium 

 nibescens, an organism he discovered in some jars 

 containing putrescent remains of animals and 

 plants which had been undisturbed for a short 

 time. The point to which he pays most atten- 

 tion is the remarkable colour of the "plastids," 

 which he considered characteristic of the 

 species. There is little doubt that it is the 



same species i tenl toned by 1 >r. ( looke in 

 his "British freshwater Algae" as Plewroeoccw 

 roseo-persicinvs Rabh., with the remark thai . 

 ■■ ct rtainly nol a good pleurococcus." He gives the 



size of the individual coll- as -0015 to '004 m. It 

 is nol mentioned in the same author's ''Introduc- 

 tion to Freshwater Algae." I do not see the reason 

 for classing this bacterium with Beggiatoa, a& 

 me it seems it would be more correctly considered 

 as a Micrococcus. 



Apart from the colour, the most interesting 'fact 

 about these lower forms of life i- that, while 

 ordinarily present to a small extent, occasionally, 

 owing to favourable conditions of environment and 

 food supply, they multiply so enormously as to 

 have the effect described. Thus giving a visible 

 example of what must occur invisibly during 

 epidemics of diseases, such as influenza and plague, 

 which, according to modern science, are caused by 

 micro-organisms distantly related to them. 



20 Fortune Green Rood, West Ha/nvpstead, 

 London, JV. W. 



AN INTRODUCTION TO 

 BRITISH SPIDERS. 



By Frank Percy Smith. 



{Continued from page 304.) 



Tapinocyba incurvata Cb. {Wakkenaera 

 incurvata in ''Spiders of Dorset.") 



Length of male 1.7 mm. 



Cephalo-thorax yellow-brown, with a green tinge. 

 Legs pale yellow, the femora being somewhat darker. 

 Abdomen black, marked with numerous impressed 

 dots. 



Tapinocyba clolosa Cb. [Neriene dolosa in 

 " Spiders of Dorset.") 



Length of male 2 mm. 



The abdomen is of a globular form. Said to bean 

 extremely rare spider. 



Tapinocyba ingrata Cb. ( Walckcnaera t'u- 

 grata in " Spiders of Dorset." 



Length of male 1.5 mm. 



Cephalo-thorax dull yellowish-brown. Legs reddish- 

 brown. Abdomen blackish-brown, tinged with green. 

 A very rare spider. 



Tapinocyba subitanea Cb. [Walckenaera 



subitaiiea in " Spiders of Dorset.") 



Length of male 1.2 mm. 



Cephalo-thorax brown. Abdomen blackish-brown, 

 tinged with olive. 



Tapinocyba praecox Cb. ( Walckcnaera 

 praecox in " Spiders of Dorset.") 



Length of male 1.7 mm. 



Very similar to T. subitanea, but the curve of the 

 posterior eyes is considerably stronger. 



