Relation betzveen Nucleolus and Chromosomes. 61 



quite certain that the nucleoli do not contribute to the formation of the 

 chromosomes and that their substance represents passive material, which is 

 of no further direct use." On the ground that in Echinus he found the 

 large vacuole of the nucleolus contractile, he regarded the latter as an excre- 

 tory organ collecting the by-products of nuclear activity. 



E. B. Wilson (1896), agreeing with the conclusion of Hacker, states his 

 opinion " that the nucleoli of the germ-cells are accumulations of by-products 

 of the nuclear action, derived from the chromatin either by direct transforma- 

 tion of its substance or as chemical cleavage products, or secretions." 



Certain observers, notably Flemming, O. and R. Hertwig, and Carnoy, 

 regard the nucleoli as storehouses of material paranuclein and plastin 

 which plays an active role in nuclear activity in contributing to the forma- 

 tion of chromosomes during division. Strasburger (1895) considers the 

 nucleoli storehouses of active material which he calls " kinoplasm," and which 

 he thinks gives rise to the achromatic part of the division figure, Hauts- 

 chicht, membrane, and cilia. 



Montgomery (1899), in his masterly work, "Comparative Cytological 

 studies, etc.," gives a very complete review of the literature on the nucleolus. 

 As the result of his own observation he is led to consider the nucleoli of egg- 

 cells and somatic cells in the Metazoa as homologous cell organs. He regards 

 the nucleoli " as extranuclear in origin, and not a secretion or excretion 

 of the nuclei . . . consisting of a substance or different substances, 

 taken into the nucleus from the cell-body." He thinks it probable that 

 " these substances stand in some relation to the nutritive process of the 

 nucleus." 



According to Pick (1899) the nucleolus is simply a storehouse or labor- 

 atory of nuclein. Bryce (1903) combines the views of Strasburger and Pick 

 in regard to the nucleolus in Echinus escnlentus. 



My study of the nucleolus (germinal spot) in the egg of Asterias forbesii, 

 both in the living and fixed condition, yields no evidence in support of 

 either Hacker's " Kernsecret-theorie" or Strasburger's " kinoplasmic" theory. 

 Nor do my results accord with the view of Bryce in so far as he adds 

 the " kinoplasmic " to the " storehouse " theory, to explain the nucleolar 

 function in Echinus. The evidence above given is conclusive, I believe, that 

 in Asterias the nucleolus is a storehouse of reserve chromatin. This is 

 demonstrated to be true by the fact that just previous to maturation connec- 

 tions are established by virtue of which chromatin material passes from the 

 nucleolus to the chromosomes and in consequence of which the latter grow 

 in size. In view of the fact that the chromosomes never really enter the 

 nucleolus, it is very doubtful whether any " idioplasm," as Rhumbler believes, 

 is stored in the nucleolus. I believe that all the hereditary elements are per- 

 sistently held by the chromosomes whatever their various size and form 

 throughout the growth-period of the eggs, and that these merely receive 



