62 Observations on the Tolles \th. 



moment to speak of the intimate structure of tliis spot, and being 

 still reserved on its genesis and function, the following is what 

 I have found : — 



(1) Generally Balbiani's nucleus is not readily distinguishable 

 in ova examined in the fresh state, or in indifferent hquids. But 

 it soon appears under the influence of certain reagents, such as 

 chloride of gold, picro-carmine, and, above all, acetic acid, 



(2) It exists in even the smallest ovules. 



(3) It is always eccentric as regards the germinal vesicle, and 

 it is generally very close to the periphery of the egg. 



(4) Its volume, which is generally inferior to that of the germinal 

 vesicle, increases with the age of the ovule. 



(5) It disappears with the maturity of the ovum, consequently 

 its disappearance precedes that of the germinal vesicle. Neverthe- 

 less, I admit this last proposition provisionally and with some doubt. 



Gand. 



II. — Observations on the Tolles' \th. 



By K. B. ToLLES, Boston, U.S.A. 



This paper is written as a supplement to what was sent the 

 Journal from Florida last month. I offer items of proof and 

 illustration not available there, the record of the ^-inch traversed by 

 Mr. Wenham in the March issue of the ' M. M. Journal ' being in 

 Boston. Of course I desired to speak accurately from the record, 

 rather than trust to recollection in any important particular. 



First, I will speak of the proof I have to offer of the claimed 

 balsam angle beyond 82° as pertaining to the -^-inch named. 



With a view to doing what I could not wait to do on the eve 

 of my departure South, I have had a ^-inch made closely to the 

 formula of the i-inch concerned. My plan for proof of outside 

 angle was to cut off or intercept all the (cone of) light entering the 

 objective — dry, by means of a central stop placed upon the posterior 

 surface of the back system. A stop of • 39" diameter accomplished 

 this, while the clear aperture of the back system being 0'44"a 

 ring of clear aperture remained, of appreciable breadth, beyond 

 the opaque circular stop. And now, observe, — with air as the 

 front external medium it is a fact no light came through the objec- 

 tive to the eye at the eye-piece. 



With no matter what obliquity, the light could not be made to 

 pass the stop to the eye. With balsamed alike with dry object 

 darkness was the effect. To test the question of admissibility of 



