186 THOMAS H. BRTCE. 



Strasbnrger regards the body as a storehouse of reserve 

 substances, which pass into the cell during division to 

 form the " kinoplasm/' which goes to form the spindle, 

 the Hautschicht, membranes, and cilia. We shall see later 

 that the phenomena observed in the sea-urchin egg 

 may combine these two views. But in contradiction to 

 both is Haecker's view. His observations on the living 

 egg of the sea-urchin reveal to him the nucleolus as a, 

 pulsating organ in which, periodically through the whole 

 growth period, small vacuoles appear ; these run into a 

 single central vacuole, which increases and then diminishes 

 in size. When the largest central vacuole appears the 

 nucleolus removes itself to the periphery of the nucleus, and 

 meantime the vacuole comes into relation with the outer 

 layers of the nucleolus, as if to bring its contents into 

 relation with the nuclear sap ; and further, an indrawing of 

 the wall of the germinal vesicle itself suggested that there 

 was a communication between the cytoplasm and nucleolus. 

 From these and other observations Haecker regards the 

 nucleolus as a secretory organ, collecting the by-products of 

 nuclear activity — not as a storehouse, or " nuclein labora- 

 torium " (Fick, 1899). So far as my observations go, they 

 tend to support the idea of the nucleolus being a storehouse 

 or laboratory of nuclein. 



Centre so me. — There has been a great deal of discussion 

 as to this enigmatical structure in the sea-urchin egg. Vary- 

 ing accounts have emanated from Boveri, Wilson, Fol, 

 Biitschli, Reinke, Hill, Kostanecki, and Erlanger. Boveri 

 says, " Das Seeigcl-Bi ist von alien objecten die von mir 

 bekannt sind, dasjeuige, welches einer sicheren Darstellung 

 der Ccutrosomen die grossten Schwierigkciten bereitet." 

 This quotation is taken from his recent Avork, * On the 

 Nature of Centrosomes.' He reconciles more or less the 

 different accounts, and suggests a nomenclature which I 

 shall adopt as being the latest and most authoritative. 



The centrosome is composed of a special and peculiar 

 substance, the ceutroplasma, which, according to the })erfec- 



