THE OVUM OF THE NINE-BANDED ARMADILLO. IO5 



I am convinced, well illustrated in the material at hand; the 

 latter has been found only in one case, but this has all the ear- 

 marks of a normal fertilization stage and is therefore accepted as 

 typical for the species, pending further evidence which may or 

 may not be forthcoming. 



During three years material for this paper has been collected 

 and studied. Ovaries of adult and young females have been 

 fixed in various fluids and studied at all stages of the sexual 

 cycle. As a rule the best stages have been obtained from the 

 ovaries of large females taken at the height of the mating season. 

 Ovaries of pregnant females show little of interest in this con- 

 nection. 



Out of a considerable variety of fixing agents used it soon 

 became apparent that by far the most efficient for nearly every 

 purpose was Zenker's fluid. Fleming's, Gilson's, Bouin's, 

 Petrunkewitsch's and formalin Zenker gave uniformly less 

 satisfactory results and were not used after the first few trials. 

 For the study of vitellogenesis the ovaries were fixed in 10 per 

 cent, neutral formalin and favorable free-hand sections weie 

 stained in Sudan III. This material, when counterstained 

 with a weak solution of methyl green was also best for measure- 

 mencs of ovocytes, as there was practically no shrinkage. 



A variety of staining processes gave satisfaction, but the 

 best for both nuclear and cytoplasmic details proved to be 

 Bensley's copper chrome hsematoxylin process. This stain 

 gives as sharp definition of chromosomes as does Haidenhain's 

 iron hsematoxylin method and in addition stains acromatic 

 nuclear materials and cytoplasmic structures admirably. On 

 account of the standard character of the iron heematoxylin 

 technique, however, this stain was used throughout as a control. 

 For certain special points several other staining combinations 

 were employed, notably toluidin blue and acid fuchsin, neutral 

 safranin and acid violet, and thyonin and erythrosin. These 

 served to bring out certain differentiations that could be dis- 

 covered only by their aid. 



