ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 147 



soluble or unobserved matter, developed from tbe organic matter of 

 the waters and made visible in a solid and insoluble form, does not 

 fall to tbe bottom, but sbows round eacb active point the sphere of its 

 activity. The gelatine keeps a record, for a time, both of the quality 

 and intensity of life in the liquid, every little centre of life making 

 itself apparent to the eye. It seems, therefore, to Dr. Smith essential 

 that all chemical examinations of water should be supplemented by an 

 inquiry, like this of Dr. Koch's, into the comparative activity of the 

 living organisms. In some waters a centre makes around it a sphere, 

 which has the appearance of a thin vesicle, and is filled with liquid. 

 These spheres form in a day or two, according to the water, and at 

 their bottom is a white mass, containing chiefly active bacteria. The 

 liquid filling the spheres may be taken out by a pipette and examined, 

 with the bacteria which lie at the bottom. Dr. Smith has not yet 

 examined a sufficient number of waters to give general rules, but 

 hopes to do so. He has as yet examined no chalk water for example, 

 but has been confined chiefly to the Manchester district hill water, 

 impure brook and pond water, Mersey, Irwell, and Medlock water, 

 and canal water. In certain specimens of Manchester water the 

 spheres appear on some days to be few in number, on other days the 

 amount is enormous, the whole of the tube in which the experiment 

 is made being filled with them. At such times the water is highly 

 impure, and complained of by the public. Dr. Smith says that when 

 the tests are sufficiently developed, " chemists must prepare for a new 

 condition of things." 



Sinel's Embryological Slides. — Sinel & Co, of St. Helier's, 

 Jersey, have issued a series of these slides, in the notice of which 

 they refer to the difficulty of preserving delicate embryological 

 objects for microscopical examination. " The favourite medium of 

 the microscopist has hitherto been Canada balsam, and owing to 

 the non-existence of a cement sufficiently powerful to hold fluid in 

 a cell, this latter medium has been viewed with some suspicion. It 

 would, however, be useless to attempt the preservation of the ova of 

 Crustacea or MoUusca in Canada balsam, but the medium used for 

 these slides, being of the same density as sea-water (and also of such 

 an admirable preservative character that the living appearance of the 

 objects is fully retained) is the most successful yet met with. 



"The slides are constructed with a cement of such power and 

 hardness that they have stood a test that would even damage a balsam 

 mount, viz. a temperature ranging from 28° to 120° F., without the 

 slightest effect upon the slide or object, and of the numbers that have 

 been prepared in this manner none have been found to leak, as is 

 frequently the case with ordinary fluid mounts. No slides are sent 

 out till they have been left some considerable time to test and 

 harden." 



The list includes the ova, in various stages of development, and 

 the young of Fishes, Mollusca, Insecta, Arachnida, Crustacea, and 

 Echinodermata, with a series of six slides of the anatomy of Palcemon 

 varians. 



L 2 



