384 The Ohio Naturalist. [Vol. IX, No. 1, 



centrosomes in question and so it seemed to me to be quite 

 unnecessary to look for them once more. Nevertheless, in order 

 to make my assertion much firmer, I made, soon after his 

 (Miyake's) paper came into my hands, a special re-examination 

 of my slides and could refind easily almost all stages of centro- 

 somes figured in "Taf." Ill, of my last paper." 



Ikeno showed his slides to Dr. K. Toyama, a zoologist, who 

 was able to see the centrosomes without difficulty. He thus 

 comes to the conclusion that the bodies which he calls cen- 

 trosomes are evidently distinct and constant structures in the 

 antheridial cells of Marchantia. 



Escoyez studjdng the same subject in 1907, makes the fol- 

 lowing statement: " Ces corpuscules du Marchantia polymorpha 

 ne sont pas de vrais centrosomes, les porteurs de cils." 



Schottlander reported the occurrence of centrosomes in 

 Marchantia in 1892. He appears to have been the first to find 

 these bodies in the Hepaticae and his methods seem to have 

 given more reliable results than some of the later attempts in 

 the same field. 



In 1900, Van Hook reported centrospheres with conspicuous 

 radiations in vegetative cells of Marchantia. These centrosomes 

 were observed in the young stalks of the archegoniophores. He 

 says that "They seem undoubtedly to exert a great attractive 

 force from the manner in which certain of the cell contents are 

 drawn to them." 



Miyake used the same methods as Ikeno. But difterent 

 manipulation seems to have given different results. It is 

 curious that with different methods I was able to obtain results 

 similar to Ikeno's. Why were Miyake and Escoyez not able to 

 manipulate the killing and staining processes so as to get the 

 same appearances as Ikeno and myself? It is evident that in 

 microtechnique the personal equation is large and similar meth- 

 ods do not give the same results to all who use them. Therefore, 

 it is useless to attempt to destroy positive evidence by negative 

 results when one cannot produce the positive which others are 

 able to obtain. 



After the appearance of Ikeno's first paper, I prepared a large 

 number of slides of the antheridiophores of Marchantia grown in 

 the greenhouse. The material was killed in the weak chrom- 

 acetic acid solution and stained on the slide in various ways. 



After much experimenting, I found that I could get the best 

 results by staining with safranin and gentian violet and then 

 restaining in Heidenhain's haematoxylin. About one hundred 

 of what appeared to be the best slides were selected for study. 

 It was found, however, that in only about ten of these had the 

 staining and clearing been done well enough to bring out clearly 



