9O C. M. CHILD. 



the utmost care as regards observations and conclusions has been 

 taken and publication has been delayed from year to year to per- 

 mit the examination of new material. In 1904 a brief account 

 of amitosis in the early stages was published. 1 Since that time, 

 however, a large amount of new material has been prepared and 

 much of the old reexamined, but without essentially altering my 

 conclusions. 



Because of the general significance of the data to be described, 

 and in order to forestall possible objections, it has seemed advis- 

 able to give in some detail the methods of preparation and pro- 

 cedure. Fresh material was fixed in May or June of four dif- 

 ferent years. In all, except the first lot of material, the animals 

 were fixed within five minutes after the sheep had been killed. 

 The first material was fixed about two hours after removal from 

 the intestine of the newly killed sheep, but all specimens were 

 alive and apparently in good condition when fixed, and results 

 showed that this material was as satisfactory as that fixed imme- 

 diately after removal from the host. 



A considerable variety of fixing agents was employed in 

 order to discover the best possible fixation and to eliminate the 

 possible effect of particular fixing agents. The fluids used in- 

 clude Hermann's, Chichkoff's, Gilson's, Perenyi's, Merkel's, 

 HNO five per cent., HNO two per cent., HNO two per cent, for 

 one or two minutes followed by Merkel for twenty-four hours or 

 more, aqueous saturated solution of sublimate, sublimate with 

 one per cent, acetic acid and Graf's chrom-oxalic mixture. 

 While certain methods of fixation proved more satisfactory than 

 others the results obtained were essentially identical in all cases 

 so far as the points in question were involved. In the work of 

 the later years Hermann's fluids, chrom-oxalic and aqueous sat- 

 urated sublimate, were most frequently used as they had been 

 shown to be satisfactory. The chrom-oxalic does not preserve 

 the delicate cytoplasmic structures in the young testes and ova- 

 ries as well as does the sublimate, but the nuclear structures are 

 equally clear in both cases. 



Various methods of staining were also employed, and while 

 the essential features are visible after almost any fairly good 



1 Child, " Amitosis in Moniezia," Anat. Am., 1904. 



