216 First ^Maturation Spindle of Allolobophora Foetida 



of the germinal vesicle of Photo. 3-1 more nearly approaches that of the 

 living egg; but the distortion of the nuclear constituents indicates the 

 injurious elfects produced by the chromo-acetic, probably due largely to 

 'the initial swelling. Snch definite and varying response to fixatives 

 serves to support the present skeptical attitude towards all cellular struc- 

 ture seen h\ fixed material. The reticulum which must represent the 

 residuum of the achromatic substance after its dehydration, presents a 

 varied aspect, definite fixatives being responsible for definite forms. 

 These form differences are clearly seen by a comparison of the reticulum 

 in Photos-. 68 to 73, Plate IV (fixed in platino-osmic) with those of 

 Photos. 51 and 52, Plate III, showing an egg of nearly the same stage of 

 development, but fixed in corrosive sublimate. The achromatic substance 

 of the former (Photos. 68 to 73, Plate IV), is a relatively transparent 

 homogeneous substance in which the chromosomes are imbedded, while 

 that of Photos. 51 and 53, Plate III, is a distinct network. The char- 

 acteristics of the achromatin of the first egg (Photos. 68 to 73) are as 

 pronounced in the unstained sections (Photos. 68 and 69) as in those 

 stained Avith iron hematoxylin (Photos. 70 to 73, Plate IV), and this 

 egg shows that dehydration and shrinkage have taken place with much 

 less distortion of the nuclear and cytoplasmic elements. The nuclear 

 membrane is intact and the cytoplasm is not torn away from the nucleus 

 as is the case in corrosive sublimate preparations, and in all these eggs 

 killed in fixatives containing acetic acid "^—compare those of Plates II 

 and III with Plates I and IV. The extent to which a fixative may distort 

 the nucleoplasm is seen in Photo. 34, 



The photographs demonstrate that apart from the nucleoli only two 

 constitutents are clearly differentiated in the germinal vesicle, the rela- 

 tively achromatic substance and the sharply chromatic filaments, which, 

 as stated above, appear to be not pure chromatin but chromatin plus a 

 part of the achromatic substance. Photos. 22 to 25, Plate II, 46, 47 

 and 59 to 62, Plate III, show in many cases clear areas around the 

 filament indicating that the chromatic filaments are partly formed at the 

 expense of the surrounding reticulum, and the fact that after some fix- 

 atives, (e. g., chromo-acetic. Photo. 34, Plate II)-, all the achromatic sub- 

 stance and chromatin are welded together, suggest that the fixative may 

 be responsible even in those cases where only a small part of the achro- 

 matic sub?tance contributes to the chromatic filament. This has a dis- 

 tinct bearing on the theory that only a small part of the chromatin of 



" Tellyesniczky's, '02, criticism of the use of acetic acid in the study of 

 nuclear constituents is supported by its effect on the egg of Allolobophora. It 

 unquestionably produces artefacts in both nucleolus and nucleoplasm. 



