( 35 ) 

 NOTES AND MEMOKANDA. 



A Microscopical Life-slide lias been described in an American 

 Journal,* which will not appear novel to some of our readers, though 

 it is described as new. It is constructed to retain the greatest quantity 

 of material under the smallest cover glass, and is designed to be used 

 with the highest powers of the microscope for studying the bacteria, 

 vibriones, and other very low forms of life. The slide consists of a 

 central polished cavity, about which is a similar polished bevel ; and 

 from the bevel outward extends a small cut, the object of which is to 

 afford an abundance of fresh air to the living things within, as well as 

 to relieve the pressure which shortly would become so great, from the 

 evaporation of the liquid within, as to cause the destruction of the cover 

 glass. No special dimensions are stated for the central cavity. The 

 bevel is usually ^ inch in diameter ; the small canal is cut through 

 the inner edge of the bevel or annular space, outward, for the purpose 

 named above. It is found upon enclosing the aninialcuhe, &c, that 

 they will invariably seek the edge of the pool in which they are con- 

 fined, and the bevelled edge permits the observer to take advantage of 

 this disposition ; for when beneath it, the objects are within range 

 of the high-power glasses. Another very important feature in the 

 device is the fact that a preparation may be kej)t within it for days or 

 weeks together, without losing vitality, owing to the simple arrange- 

 ment for supplying fresh air. " We," says the writer, " have repeatedly 

 had the opportunity of witnessing the use of this slide, and are con- 

 vinced that nothing of the kind has yet been devised which can equal 

 it in excellence either for observing or generating the lower forms of 

 life." 



A Review of the " New Conspectus of the Families and Genera 

 of Diatomacese," by Professor H. L. Smith, has been published in 

 ' Grevillea,' by Mr. F. Kitton, in which he says that the Professor " has 

 applied the pruning knife most unsparingly, doubtless to the great 

 disgust of the ' species mongers.' Some of the genera might, he thinks, 

 have been retained with advantage ; for example, the Campylodisci, 

 which have been relegated to the Surirellse. This genus has two 

 unvarying characteristics, viz. the circular form of the valves, and 

 the median space of the two valves of the frustule are always at 

 right angles to each other ; consequently the valve must be truly 

 circular. Professor W. Smith, the author of the ' Synopsis,' has 

 erred in placing Camjpylodiscus spiralis in that genus. Kiitzing was 

 right in making it a species of Surirella (S. spiralis). The union 

 of the genera Triceratium and Amphitetras with Biddulphia wo 

 think will not be generally accepted ; to do so necessitates the 

 enlargement of the generic characters of the last to too great an ex- 

 tent. The number of species will also be inconveniently large. The 

 genus Triceratium might, we think, be united to Amphitetras without 



* ' Journal of the Franklin Institute.' 



