DUBLIN NATimAL DISTOEY SOCIETT. 213 



in these specimens kept for some time on a slide. Notwithstanding 

 their not very unusual appearance, for the absence of the central septum 

 was not very striking, and might not be noticed at first sight, unless 

 closely looked into, as well as there being no external aberration in form, 

 it appears to me that the specimens of Penium cylindrus alluded to were 

 so many illustrations of the same abnormal mode of growth, extreme 

 cases of which I have tried to depict in the drawings. For I cannot 

 easily understand, without the original separation of the primordial 

 utricle with the contents, and the formation round it at the ends of new 

 cell- wall, how an articulation could exist to allow of the ultimate sepa- 

 ration into two fronds of the old segments with the portion that should 

 appertain to each of the newly grown structure. 



What causes the change in the direction of the axis of growth in 

 the specimens represented by some of the figures, does not appear to me 

 so readily to be accounted for. In each case I should suppose the plant 

 would cease to grow, and the abnormal individual perish, unless, indeed, 

 each or any might be supposed to possess the power of afterwards fonn- 

 ing a septum at the suture connecting the newly- grown portion with 

 the older segments, a second new growth becoming then interposed, and 

 the central misshapen structure thus becoming eliminated. 



Mr. Horatio Yeates sent for exhibition to the Society a new micro- 

 scope-stand of his construction, and in his absence it was kindly brought 

 forward and shown to the meeting by the Rev. Eugene O'Meara, who 

 drew attention to the modifications adopted, and explained their pur- 

 pose. This is an exceedingly simple and ingenious little instrument, 

 supplied with a rotatory stage, and combining its advantages with that 

 of obviating any necessity for centering. The compound body is firmly 

 attached by an oblique arm to the mai'gin of the rotatory stage, and, 

 revolving adong with it, the optical axis of the instrument thus alwaj-s 

 remains in the same relative position in regard to the object. The mir- 

 ror is attached to a radius bar fixed at the back of the stage, thus afibrd- 

 ing any degree of obliquity of light, and permitting its use above the 

 stage for opaque objects. The stage does not possess vertical or trans- 

 verse movements, but these, if required, could readily be added ; and, 

 doubtless, amongst the recommendations possessed by this instrument, 

 tliere might be counted the greater cheapness with which it could be 

 produced, as compared with much larger microscopes, of higher preten- 

 sions, involving costly contrivances for accomplishing the foregoing ends. 



Mr. Sanders said he had been much pleased by an inspection of 

 Mr. Yeates' new stand, which, not only from its simplicity, but from its 

 apparent adaptation to the purposes in view, seemed calculated to become 

 very valuable to the microscopist. It had always been a desideratum in 

 several departments of research, to be able to cause the object to revolve 

 so as to expose each side of it successively to the light; but which, owing to 

 the inevitable imperfection of even the best workmanship, was difficult 

 to accomplish without involving much trouble and loss of time in ad- 

 justing the centering of the body of the instrument in regard to the ob- 



