386 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



related to physodes. Swingle found them in some of the 

 Saprolegniales and certain Rhodophycese and Lagerheim in 

 Ascoidea. They are probably not uncommon. Nematoplasts- 

 may be proteid crystals but there is evidence that they move, 

 bending slowly back and forth, which suggests a higher degree 

 of organization. They should be further studied. 



Physodes are bladder like structures described by Crato, '92,. 

 in certain brown Algae. They contain a highly refractive sub- 

 stance which gives them a very different appearance from 

 vacuoles whose structure they resemble in many respects.. 

 Very little is known about the contents of physodes and it may 

 well be questioned whether they are really organs of the cell 

 and not vacuoles set apart to hold some fluids or substances 

 other than cell sap. 



There are left for us a group of kinoplasmic structures that 

 are especially prominent and sometimes only present during the 

 events of nuclear division and at the times when cilia are 

 formed. They will be discussed in later sections of these papers- 

 (Sections II, III, V and VI) and at this time we shall give but 

 a brief statement of their appearances. They are centrospheres,. 

 centrosomes, asters, filarplasm and blepharoplasts. 



Centrospheres are rather large areas of kinoplasm that some- 

 times lie at the poles of nuclear figures and to which are 

 attached the fibrillse that form the spindle and also those that 

 may radiate into the surrounding cytoplasm. If the centre- 

 sphere contains a distinct central body, or if such a small 

 structure be present alone at the poles of the spindle it is called 

 a centrosome. Should either structure be accompanied by 

 definite fibrillar radiations the whole is termed an aster. These 

 latter conditions are sometimes very complex and are the most 

 interesting types of structures. Asters with centrosomes are 

 known for the brown algae in the growing points of Sphacelaria 

 (Fig. 3c), Stypocaulon (Swingle, '97) and the spore mother cell 

 of Dictyota (Mottier, :oo). They are also beautifully shown in 

 certain diatoms (Lauterborn, principal paper '96, Karsten, :oo). 

 Asters with centrospheres and occasionally but not constantly 

 containing centrosome-like bodies are found in the oogonium 

 and germinating eggs of Fucus, see Fig. 3, d (Strasburger, '97",. 



