Mitotic division of the nuclei of the Cyanophyceae. 



Edgar W. Olive. 



With plates I— II. 



One of the most eagerly investigated as well as one of the 

 most confused problems connected with recent cytological re- 

 searches is that concerning the cell Organization of the Cyano- 

 phyceae. Is there a cliromatophore ; and if so, what is its natura ? 

 Does the cell possess a niicleus, or is it a non-nucleated organism? 

 If the so-called „central body" is a nucleus, then is its division 

 dii-ect or indirect? These constitnte the main dispnted questions. 

 Even after the exhaustive stiidies of Fischer (97), Hegler (Ol), 

 Kohl (03), Wager (03), and others, the real nature of the 

 central body has been regarded by the majority as still open 

 to question. 



In attempting a comparison of the relations of the chromatin 

 in the nuclei of many of the lower plants, the writer found 

 that tliin sections of various Cyanophyceae showed with compar- 

 ative clearness the internal structui"e of the cell, and also made 

 quite evident the nuclear nature of the central body. Furthermore, 

 the most modern methods of fixation and staining, as one would 

 expect, have proved entirely successful, contrary to the statements 

 of Hegler, who asserts that the usual methods were not successful 

 in procuring a sliarp differentiation. In fact, it has been demon- 

 strated to the writer's complete satisfaction that the Hegler 

 method of fixation itself gave, on the other liand, extremely poor 

 results; and the conclusion has been reached, after mucli trial, 

 that it is only by means of thin sections, properly stained, that 

 certain important details of the cytology of these minute orga- 

 nisms can be made out. 



The writer naturally liopes that in the present paper this 

 difficult (piestion has been brought somewhat nearei- Solution. 

 As will be seen, however, the subject is regarded as far froni 

 closed, especially from a physiological point of view. Two 

 papers have just appoared, the very exhaustive one by Professor 

 Kohl and the long promised one by Mr. AVager, and it has 

 therefore been thouglit advisable to publish some of the results 

 of this investigation at once, before it is fully completed. Some 



