180 



♦ KNOWLEDGE ♦ 



[Sept. 21, 1883. 



more or less open to very serious objections, either on 

 account of their mechanical details, or because they fail 

 after a time to " fulfil their f mictions " adequately. In the 

 tirst form of filter just alluded to, the working portion is 

 securely cemented down, and when it requires to be cleansed, 

 an amount of delay and expense is occasioned which is 

 often very disheartening to the unfortunate possessor. The 

 second variety consists either of a solid mass of porous 

 carbon, or other material filled in to produce a dense aggre- 

 gate through which the water is made to pass. It is 

 obvious that, in these arrangements, there is a tendency for 

 the filters to become " foul " through the accumulation of 

 noxious materials within their porous recesses, which then 

 necessitates a laborious cleansing process. 



It is a prevalent notion amongst those who have not 

 paid any attention to the subject, that drinking water 

 harbours countless strange organisms which pass collectively 

 under the name of " animalcule'," very likely for the same 

 reason why Rotifers, Diatoms, and Desmids were classed 

 together with the Injusoria by the earlier microscopists. 

 Doubtless this popular belief had its origin in such pictures 

 as Fig. 17, taken from Dr. Hassall's valuable little work 

 on " Food and its Adulterations," as well as from indis- 

 criminate displays of a drop of stagnant water under the 

 microscope at Sunday-school soiries, or other delightful 

 heterogeneous gatherings. But, when it is known that 

 these monstrous-looking creatures can be captured from 

 drinking water only after diligent search and Ijy straining 

 oceans of the water, and that only in very ill-conditioned 

 water do they congregate in numbers, much of the ardour 

 and wonderment of the inquiring novice is dispelled, and 

 he feels that he is disappointed because he does not actually 

 swallow a few millions of them with every tumbler-full of 

 water. 



Fig. 17. — A, animal and vegetable productions contained in the 

 water of the Thames taken at Richmond. B, organic matter, 

 living and dead, especially the Thames Paramceciv.m and husk of 

 wheat (from Hassall). 



Nevertheless, it is a patent fact that these minute forms 

 of life do live and thrive in drinking-water, a fact attested 

 to by Fig. 18, which is also taken from Dr. Hassall's 

 book.* Some of these little creatures are harmless ; 

 indeed, they are even useful, in endowing the water with 

 a certain palatable freshness through the gases which they 

 eliminate ; but others — and alas ! by far the larger propor- 

 tion — are highly deleterious. Take, for example, the 

 Paratiuecia in Figs. 17 and 18 ; they are the invariable 

 concomitants of decaying vegetable matter, and are often 

 accompanied by minuter forms, whose very names, Bac- 

 terium, Bacillus, kc, have recently been associated with 

 the most virulent maladies which " flesh is heir to." Most 

 of them have already been described in these pages by 

 Mr. Slack ; we therefore refer the reader to his ^excellent 

 articles.t 



* We are indebted to Mr. Maignen for the use of these figures, 

 t r^ supra June 1st, June 20th, and July 13th, 1883. 



Fig. 17 shows, that beside living creatures, water is apt 

 to contain foreign particles of dead matter in various stages 

 of decay, such as the husks and straws of wheat, &c., and 

 inorganic particles — e.g., sand, itc. Whilst mostly harmless 

 in themselves, they aflbrd food and shelter to the more un- 

 welcome living things. At all events, everybody will 

 admit that, taking all these circumstances into considera- 

 tion, it is desirable to free the water from them by some 

 means, and then to try to render that water palatable. 

 Both of these ends are met by Maignen's filter, which 

 purifies, and at the same time aerates, the water. Although 

 we have seen the exhibitor quaft' from a glass of purified 



Fig. 18. — A, Watee t.^ken from Cistern, a, blood-red Annelids; 

 h, Brachionus polyacanthus ; c, Euplotes charo7i ; d, Paramoicia ; e, 

 Amphileptus ; f, Actinophrys Sol ; g, Actinophrys viridis ; h, Pedia- 

 strum Boryanum; i, Closterimn Lunula; k, Scenedesmus quadri- 

 canda ; I, Scenedesmus aciitus ; ■m, Scenedesmus ohtusus ; n, Cyclo- 

 tella operculata ; o, Nitzchia Sigma ; j). Sy7iedra minutissima ; r, 

 Melosira varians ; s. Threads of slender fungus ; t, Minute star- 

 shaped bodies ; r, Organic and earthy matter. Mag., a 12 ; ft 100, 

 the rest 200 diameters. B, Watek taken fro.m Service Pipe. 

 e, Paramcecia (2 species) ; b, Vorticella convallaria ; c, Coleps 

 hirtus ; d, Pandorina Moruvi ; e, Scenedesvius quadricanda ; f, 

 Naricula Amphishcena ; g, Navicula sphxErophora ; h, Asterionella 

 formosa ; i, Fragilaria Capuoina ; i'. Brown active sporules ; I, 

 Stationary green sporules ; m, Threads of slender fungus ; n, 

 Organic and earthy matter; o, Anguillula fluvialis. 



sewage which had simply passed through the patent inven- 

 tion, yet we are inclined to advise a previous boiling of the 

 water, to ensure the death of such things as Bacteria. The 

 aerating tube, C, Fig. 16, may also be loosely plugged with 

 cotton wool, so that stray germs can be intercepted, and if 

 a cork be fitted into the aperture so prevent aeration, the 

 filtered water we have found to be admirably adapted to 

 the wants of a naturalist's laboratory, where distilled water 

 is not always necessary. 



The next series of exhibits which demands our attention 

 is that comprised under the head Ccelenterata, with its two 

 principal classes, the I/ydrozoa and the Actinozoa. A 

 C ct'Jenti'rate animal consists essentially of a sac-like body, 

 the walls of which are primarily composed of two layers, an 

 outer, ectoderm, and an inner, endoderm. There is gene- 

 rally a radial arrangement of parts, observable chiefly in 

 the tentacles with which nearly all of them are provided ; 

 and, although they do not possess any marked ner\'Ous 

 system, they are characterised by the presence of " thread 

 cells," or peculiar urticating organs, used as weapons of 

 oflence and defence. It will be seen from this definition 

 that they approach very nearly to some of the sponges, 

 and their reproductive processes, both by gemmation and 

 division, as well as in the simpler forms of sexual genera- 

 tion, link the two groups together still more closely. 



At Stand 75G, a series of microscopes, under the care of 

 Mr. Bolton, of Birmingham, are invariably supplied with 

 living forms of one of the simplest, and certainly most 

 beautiful, of the ILjdrozoa — viz., Hydra viridis, or the 

 fresh-water polype. The little Hydra consists of a simple 

 cylindrical green sac-like body, closed at one end, which 

 serves to attach it at the will of the creature to some 



