282 Dr. Barry oti the Mode of Origin of the Cell-membrane, 



As the correction in the distance for S, is approximately equal 

 to the correction in altitude of Sj rnultij)lied by the cosine of the 

 angle QVT, on VT take from scale the correction of S, in alti- 

 tude = VM, draw NM parallel to QT, then VN is the correction 

 in distance on the same scale approximately. 



In the same way the angle ZSjSj may be measured, and the 

 correction of the distance due to the error of altitude of Sg may 

 be found. 



When the point Z is placed at C the centre of the picture, the 

 angle on the picture S,ZS2 is equal to the original angle SjZSg. 



The point Z may be placed anywhere in the picture, and the 

 proper construction may be inferred from what precedes ; but 

 then the circle described with radius ZSg will be replaced by a 

 conic section, and the angle SjZS^ will not be equal to the original 

 angle SiZSj. 



XXXVII. — I. An Attempt to show the Mode of Origin of the 

 Cell- Membrane, and the Nature of tJie Earliest Pores. 



II. Remarks on the Article " Ovum " in the Cyclopedia of 



Physiology. 



By Martin Barry, M.D., F.R.S.* 



[With a Plate.] 



THE discoveries of Keber on the porosity of bodies have re- 

 minded me of some drawings of mine from nature, which 

 lie buried in two rows of figures at the foot of a Plate in the 

 Phil. Trans, for 1841 f; — drawings which, from some remarks 

 I made at the same time, it will be seen that I then believed to 

 illustrate the mode of origin of the membrane of the cell J. 

 Further, there being among those drawings one which has long 

 seemed to me to present the earliest pores, I will reproduce a 

 few of them on this occasion. 



There is first seen a large mother-cell. The nucleus of this 

 divides into many parts — each part being itself a nucleus. From 

 their origin in a mother-cell, these nuclei, after their liberation, 

 are found in groups. They form cells, which are elliptical at 

 first, become more spherical, and are often seen to be tapered 

 at one end. (What the cells in question are, will be stated 

 further on.) 



Plate II.* fig. A represents one of the nuclei now mentioned as 

 arising from division of the nucleus of a mother-cell. It has a nu- 

 cleolus. At B such a nucleus has become segmented, and that 



* Communicated by the Author, 

 t Plate 25, figs. 164 to 173. 



X Phil. Trans. 1841, p. 243. § 193. See also in the same volume the 

 description of figs. 1/0 and 171, in the explanation of the plates. 



