30 THE CELL DOCTRINE. 



that an actual growth of the elementary parts of epi- 

 thelium took place without vessels. 



Taking up the nucleus as discovered by Robert 

 Brown, Schleiden,* in reference to its function, ap- 

 plies the name cytoblast (*yroc, a cell, /5Aa<rro^ a 

 bud or sprout), or " cell bud," and in a careful study 

 of its anatomy, discovers that "in very large and 

 beautifully developed cyloblasts, there is observed 

 a small, sharply defined body, which, judging from 

 the shadow which it casts, appears to represent a 

 thick ring, or thick-walled hollow globule. "f One, 

 two, three, and even four of these may be present. 

 Without further present comment than that these 

 characters, as given by Schleiden, are by no means 

 constant, it is plain that what is commonly known 

 as the nucleolus is here intended, to the discovery of 

 which we are therefore indebted to him, though 

 Valentin also claims its discovery at an earlier 

 period.! He further states that the observations he 

 has made upon all plants, lead him to the conclusion 

 that these small bodies are found earlier than the 

 cytoblasts. 



According to Schleiden, when starch is to be em- 



* Schleiden, Beitrage zur Phylogenesis, Muller's Arehiv, 1838, 

 p. ii ; Contributions to Phytogenesis, Sydenbam Soc. Transl., p. 

 233. 



f The term nucleolus or nucleus-corpuscle (Kernkorporchen), 

 seems to have been first applied by Schwann. (See Introduction 

 to Schwann's Researches, Syd. Society's Translation.) 



J Valentin, " Outline of the Development of Animal Tissues," 

 in Wagner's Elements of Physiology, Translated by Dr. Willis. 

 London : 1844, p. 214. Leipzig : 1839 ; where he refers to Val- 

 entin's Repertorium, vol. i, p. 143. 



