114 MUNSON. [Vol. XV. 



Methods. — The best preserved material of the young forms 

 was obtained by killing in (i) Kleinenberg's picro-sulphuric, 

 (2) corrosive-acetic, and in (3) a mixture, in equal parts, of 

 a ten per cent solution of nitric acid and picro-sulphuric. 

 Material killed in this latter mixture was excellently preserved. 

 It has the advantages of staining readily, and is especially 

 suited to the double stain of Lyon's blue and lithium-carmine. 

 By this means, the archoplasm and centrosomes are made very 

 distinct. It was not so favorable for the study of the various 

 phases of karyokinesis. For this, material preserved in Mer- 

 kel's fluid was used. 



The ovaries of the adult animal successfully preserved in (4) 

 Merkel's fluid are excellent for the study of the centrosomes 

 and sphere. This fluid, however, does not always give equally 

 good results, even when most carefully applied. Slight irreg- 

 ularities in the preparation of the mixture, as well as differ- 

 ences in temperature, may account for some of the differences 

 in the effect ; but physiological variations in the egg itself, 

 especially those changes arising from a constantly increasing 

 quantity of food material, are perhaps responsible for much of 

 the variation. 



In that stage of the egg immediately preceding its escape 

 from the follicle, the following method was successfully em- 

 ployed : (5) one-fourth per cent aqueous solution of platinum 

 chloride applied for twenty-four to forty-eight hours, and the 

 eggs then passed through the various grades of alcohol. The 

 eggs may also first be killed by leaving them a few minutes 

 in Flemming's fluid and then transferring them to platinum 

 chloride for forty-eight hours. 



For the stages of the mature egg, after it gets into the ova- 

 rian tube, Kleinenberg's picro-sulphuric has been found most 

 favorable, where attempts to imbed in parafifine have been made. 



Owing to the difficulty of staining after Flemming's and 

 Hermann's fluid, these have not been extensively used, 

 although a number of the drawings have been made from 

 preparations of material preserved in this way, as well as 

 from material hardened in corrosive sublimate, corrosive- 

 acetic, and picro-sulphuric. 



