68 MEMORANDA. 



reason to believe so as Dr. Pouchet has for assuming that 

 when a suitable infusion is exposed to the air, the " ova" of 

 infusoria, or the infusoria themselves, spring into life byspou- 

 taneous generation. The value of this portion of his evidence 

 "would have been better appreciated if he had stated accurately 

 of what substances his suitable infusion consisted, whence 

 the substances were obtained, what species of infusoria made 

 their appearance, and after what lapse of time the first ap- 

 peared. 



Dr. Pouchet, as a physiologist, would not wittingly seek to 

 uphold an erroneous theory simply because he had formerly 

 espoused it as correct. 



No doubt he and others will again give it an unprejudiced 

 trial, and it appears to me that there are various ways of 

 arriving at a satisfactory conclusion. 



Any one, even without a laboratory at his disposal, may 

 verify or controvert the statement of Professor Schultze. 



The exposure of vatious dissimilar infusions to the atmo- 

 sphere in the same place, and of similar infusions in different 

 places (care being taken in every case that the germs of life 

 are extinct in the substance exposed), and the examination of 

 the living forms that appear in them, would also aid in sohdng 

 the problem. If the latter expedient be resorted to, it would 

 be as well to bear in mind that, in the infusion of cabbage 

 juice and distilled water exposed by me in the neighbour- 

 hood of Hull, the form that presented itself (alone, so far as 

 my memory serves) was Glaucoma scintillans. 



Without reference to the question of " spontaneous genera- 

 tion," I feel satisfied that good results Avonld follow from a 

 repetition of these experiments ; for the observer must neces- 

 sarily watch the development of different forms of animal and 

 vegetable existence, and in so doing he would not only obtain 

 a clearer insight into this organisation, but would, in all pro- 

 bability, be able to add to the small stock of information that 

 we possess on this interesting branch of natui'al history. — 

 James Samuelson. 



thin Stage for the Microscope. Constructed ty Thomas 

 Soss.— D D is a dovetail plate affixed to the main body or box 

 of the instrument. In this works the fitting c, which has a 

 strong bar, e e, at right angles to it (all one casting) . Motion 

 is given to the fitting, c, by means of the screw b. a, milled 

 head fastened to screw ; this screw works in a spring box, 

 which prevents loss of time. On the bar, at right angles to 

 c, moves a strong-fitting box, k k, to which motion is com- 

 municated by the milled head and pinion g. Surmounted on 



