No. 466.] STUDIES ON PLANT CELL.— VIII. 713 



But the manifestations of kinoplasm during nuclear division 

 and also in relation to cilia-bearing surfaces are exceedingly 

 various and it is among these structures that our ignorance of 

 relationships and modes of origin is deepest. These kinoplasmic 

 structures have been described in various connections through- 

 out this series of papers and especially in Sections I, II, and 

 III, and need not be treated here. But the point which should 

 be emphasized in this connection is the necessity of the close 

 study of their simplest expressions in the lower regions of the 

 thallophytes. The most varied forms of kinoplasm are in the 

 thallophytes where asters, centrospheres, and centrosomes ob- 

 tain and where ciliated cells, presumably with blepharoplasts, 

 may occupy long periods of the hfe history. It is here that we 

 must search for information that will bring order out of the con- 

 fusion of our present accounts and insufficiency of knowledge. 

 The most vital problems relating to kinoplasm concern the ori- 

 gin and the events of the simplest types of mitotic phenomena 

 and the formation of cilia. We have a fairly clear understand- 

 ing of the general features of mitosis in the groups above the 

 thallophytes and their relation to the lower types and these will 

 be briefly treated in the following portion of this section under 

 the head: "Some Apparent Tendencies in the Evolution of 

 Mitotic Phenomena." But the events of mitosis among the 

 thallophytes are exceedingly various and difficult to understand 

 and nothing is known of their origin or relation to the simpler 

 conditions which must be present in the lowest regions of the 

 Chlorophycese and in the Cyanophyceae. 



Trophoplasm comprises all of the cytoplasm included within 

 the plasma membranes. While this region does not give rise to 

 such highly differentiated cell organs as the kinoplasm, never- 

 theless some remarkably interesting structures are developed. 

 Ccenocentra and Physodes are specialized structures of exceed- 

 ing interest and our ignorance of the latter is truly remarkable. 

 Nematocysts if trophoplasmic offer another attractive subject for 

 investigation. In a sense, chrortiatophores and plastids may be 

 considered trophoplasmic but their high grade of specialization 

 and fixity as cell organs gives them a certain independence of 

 other structures in the cell. Respecting the structure of the 



