58 PROCEEDINGS OF SOCIETIES. 



same Hydra, but sometimes there were sperm cells only, when the whole 

 body was seen to be studded with them. The diameter of the ovum was 

 about ^'oth of an inch, that of Hydra viridis about ^th. Hydra vulgaris 

 is reproduced from ova in the autumn, Hydra viridis in the spring. 



Mr. Ingpen exhibited and described an achromatic bull's-eye con- 

 denser, formed out of the objectives of a binocular opera-glass. One 

 of the lenses w^as reversed in its cell, and the two screwed into the 

 opj)osite ends of a short j)iece of tube, so that the flat side of one 

 nearly touched the convex side of the other. The light thrown by 

 this condenser was very pure, and those who possessed a binocular 

 opera or field-glass could construct one at a small expense, while the 

 lenses were not spoilt for their original purpose. 



The President announced that at the next meeting he would read 

 the fifth of his series of papers " On the Histology of Plants." 



The meeting concluded with the usual conversazione, at which 

 several interesting objects were exhibited. 



May 22. — Dr. Eobert Braithwaite, F.L.S., President, in the 

 chair. 



Twenty-three members were duly elected. 



The death was announced of Mr. T. W. Burr, F.R.A.S., F.E.M.S., 

 an old and valued member and a Vice-President of the club. 



Dr. George Hoggan read a paj)er " On a New Section-cutting 

 Machine." This instrument differed in many respects from any of 

 those in ordinary use, and was designed by him for cutting both hard 

 and soft substances. Two of these instruments were exhibited, and 

 minutely described. A stoi;t plate of brass, sliding in a double dove- 

 tailed gi'oove, was moved backwards and forwards by a micrometer 

 screw. Upon this plate the substance to be cut, if hard, was fixed by 

 one or more clamps ; if soft, it was inserted in a cube of carrot, cut to 

 fit a brass trough, which could be similarly clamped to the plate or 

 " table," so as to move with it. Hard substances were cut with a very 

 fine- toothed spring saw, which was guided between strong supports, so 

 as to be capable of cutting a series of perfectly parallel sections. In 

 one of the instruments shown, there were three of such sections from 

 a tooth, cut very nearly through, but still attached to the rest, from 

 which many more sections could be made. These sections were 

 ready for mounting, the saw marks being scarcely, if at all visible. 

 Stress was laid ujion using the saw with the teeth reversed, so as to 

 cut while pulling, and not while pushing it. Soft substances, after 

 being imbedded in the cube of carrot, and wedged up, if required, 

 with pieces of elder-pith, were fixed to the plate by means of the 

 trough, and the knife or razor was guided by two parallel bars of 

 steel, instead of sliding over a plate, by which method the edge was 

 less liable to injury, and sections of large masses of imequal con- 

 sistence could be cut with great facility, from the possibility of 

 making a number of short cuts, instead of single sweeps only. The 

 blade of the knife was straight, the under side flat, and the uj)per side 

 deeply hollowed, so as to contain enough fluid to float off the section 

 as soon as it was cut. The machine was rather complicated, but this 

 was necessary, from the desire that success should depend as little as 

 possible upon the skill of the operator. 



