No. 3-] THE EGG OF ALLOLOBOPHORA FOETIDA. 139 



pared to discuss the finer details of these structures, for we 

 feel we must wait until we can control the shrinkage of the 

 eggs killed in osmic acid, before placing much confidence in 

 the morphological details seen in sections. This shrinkage 

 occurs in the alcohols. When formalin is substituted as a 

 hardener, the shrinkage is much reduced, but the use of 

 formalin prohibits sharp staining. The spinning phenomena, 

 which has been seen by Mrs. Andrews (i) during the formation 

 of the polar bodies in other eggs, we have not yet been able to 

 detect, but in view of the exceptional cases in which we have 

 seen the chromosomes and other details in the living Qgg of 

 Allolobophora foctida, we are not prepared to say that the above- 

 mentioned spinning phenomenon does not occur. 



Shrinkage. — A comparison of the size of sections of eggs 

 at a given stage with the size of the average living o.^^ at the 

 same stage shows that, at some point or points in the tech- 

 nique, a large amount of shrinkage has occurred, in some cases 

 amounting to one-half the diameter of the living eggs. With 

 a view to determine when the shrinkage occurs, we have first 

 measured the living egg and then each step in the subsequent 

 technique. In this manner we have tested twenty-eight fixa- 

 tives, the compound fixatives and their component parts, each in 

 varying strengths and varying the time the egg was immersed 

 in the fixative from five minutes to twenty-four hours. An 

 attempt to formulate the data gathered from these experiments 

 has shown that the action of a given fixative upon eggs, even 

 at the same stage of development, is extremely inconstant. But 

 as a general rule, subject to many exceptions, it may be said : 

 First, certain fixatives shrink the living Q.%g, and in these cases 

 relatively little shrinkage is produced by the subsequent treat- 

 ment with the alcohols, e.g., strong chromic acid and, in most 

 cases, corrosive acetic (strong). Second, certain fixatives do 

 not shrink the living Q-gg, and in these cases they shrink more 

 or less during the subsequent treatment with alcohols, e.g., 

 weak osmic acid, .1^ to i^, and corrosive sublimate. Third, 

 certain fixatives swell the living ^%%, the subsequent treatment 

 with alcohols producing a slight shrinkage — the final result 

 being a mounted ^gg with almost the same diameter as the 



