THE RELATION BETWEEN AMITOSIS AND MITOSIS. QI 



nuclear stain, Heidenhain's iron-haematoxylin was most com- 

 monly used because of its well-known sharp definition. Un- 

 doubtedly this stain is of little or no value for determining 

 differences of chemical composition but it is certainly unsurpassed 

 for bringing out physical differences. Almost the whole body 

 of one worm from the scolex to the region where the uterus 

 contained late cleavage stages was sectioned. From other chains 

 pieces containing three or four proglottids were taken at intervals 

 of from ten to forty proglottids, throughout the body. Pieces 

 separated by thirty or forty or even a larger number of pro- 

 glottids give stages so near together that nothing is lost, but 

 since it was necessary to make certain that mitosis did not occur 

 periodically in certain regions the intervals between pieces were 

 made much shorter in certain cases. The pieces intervening 

 between those sectioned were numbered and kept and frequently 

 some of them were sectioned later when a larger number of 

 cases of certain stages was needed or some point remained to be 

 settled. Every piece sectioned included at least two complete 

 proglottids and usually more, in the anterior regions often fifteen 

 or twenty. Sections were cut 35 // thick. 



New material was sectioned and examined in four different 

 years and each year the old material was reexamined. Some 

 four hundred camera drawings of nuclei or groups dividing 

 amitotically have been made and in all cases the greatest care 

 has been taken to select those cases which were most clear and 

 convincing. Cases which might possibly be interpreted as 

 amitosis were recorded only when they formed part of a region 

 included in a drawing made for other reasons. The cases 

 recorded by special drawings were usually those which it seemed 

 impossible to interpret in any other way. Many of the cases 

 from which drawings were made were examined by other persons 

 and their interpretation agreed with my own. The observations 

 were 'all made with a 2 mm. oil immersion lens. With this 

 power some of the divisions may be seen with almost diagram- 

 matic clearness provided fixation and staining are satisfactory. 



So far as I am aware I have employed every possible means 

 to establish my observations and to eliminate errors. Amitotic 

 division is not as readily distinguished as mitosis, for there are 



