Animal and Vegetable Fibre. 323 



off its substance, and continually renewing it.* In the so- 

 called cytoblast as well as in the nucleus of the cell, the nu- 

 cleolus is the prime mover. It is more than the prime mover, 

 for it passes into fibre. The " cytoblast' 1 that forms a coil, 

 and the nucleus that unwinds itself like a ball of twine, 

 really represent the nucleolus enlarged. The nucleolus thus 

 enlarged passes into fibre ; and it passes into nothing else, 

 it always passes into fibre. It is therefore not enough to 

 say that the nucleolus is the prime mover. It is far more 

 than this. The whole organism arises out of nucleoli. For 

 fibre is but the nucleolus in another shape, and every struc- 

 ture arises out of fibre. 



This reproduction of the nucleolus by self-division, — its 

 continually giving off its substance, and continually renewing 

 it, — and its passing into fibre, which by the self- division of 

 its filaments forms the whole organism, — are facts which it 

 was impossible to become aware of, without being reminded 

 of another fact, made known by my " Researches in Embry- 

 ology," t that the point of fecundation in the ovum is also a 

 nucleolus, which after fecundation is likewise, and continues 

 to be, reproduced by self -division. For in this continued 

 self-division of nucleoli endowed with the properties in ques- 

 tion, — this descent, as it were, of properties from one nucleolus 

 to another, — there is to be recognized a fact, I think, not 

 undeserving of notice in connection with the subject of re- 

 semblance between the offspring and its parents. 



* This is an important point, essential to an understanding of the physiology 

 of cells. When describing the " cytoblast" in a former paragraph as at first 

 a minute particle, I stated that there occurred no deposition of granules around 

 it, as many had imagined. They were right in supposing a smaller body to 

 exist before the larger one, but wrong in imagining the larger body to arise 

 from deposition of a substance around the smaller. Observers thought that 

 their nucleolus in the " cytoblast" was identical with the previously existing 

 smaller body. It is not so. The previously existing smaller body absorbs and 

 assimilates new matter and becomes the " cytoblast." To some this difference 

 may seem small. It is far otherwise, and essential to an understanding of the 

 properties of the nucleolus. (See my " Researches in Embryology, third series ; 

 a Contribution to the Physiology of Cells," Phil. Trans. 1840.) 



t Phil. Trans. 1840. 



x2 



