The Prophase in the Ovigenesis and the Spennatogenesis of Planaria etc. 435 
parts) in 40^ alcohol. This solution should be of a rieh brown-red 
colour. The slides are then washed in water. Then immersed in (a) 
Saffranin 0. (satnrated solution in lb% aleobol) for 4 hours, then 
washed in water and immersed in (1» Methylene-blue (a solution 
made up as follows, 7 gr. Methylene-blue l / 2 Bicarbonate of Soda, in 
100 cc. distilled water) for 5 to 15 minutes; then washed in water 
and brought up through rising grades of alcohol to (c) a solution 
of Orange G. in Clove Oil. This is the differentiatiug fluid, and the 
slides should be left in until sections have a pale blue colour. The 
cytoplasm is stained orange. Cytoplasmic reticulum blue. Chromatin 
purple, nucleolus red, centrosomes red. Except when otherwise stated 
all the figures liave been drawn from preparations stained with this 
triple stain. 
2. This triple stain may be varied by using for (a) a satnrated 
solution of Basic Fuchsine in 75^ alcohol. But in this case the 
Methylene-blue is more basic than the Fuchsine. Chromatin is bright 
blue, nucleoli bright red, cytoplasmic reticulum and connective tis- 
rue red. 
3. Thionin and Orange G. The Thionin should be a saturated 
solution in 70_^ alcohol. This stain does not sliow up the yolk globules 
in the oocytes. 
4. Heidenhain’s Iron-Alum Haematoxylin. 
PART I: — The resting nucleus and prophase in the ovigenesis of 
Planaria lactea. 
The ovigenesis in the Freshwater Planaria has been worked out 
by E. Mattiesen for Planaria torva ( 04) , and by W. Schleip for 
PL qonocepluda (’06), and also in a new species PL simplicissima bv 
€ürtis (’OO). 
The description of the earlier stages of the maturation ditfers 
not inconsiderably in the work of the first two authors, and my results 
differ from theirs in some important particulars, which will be referred 
to in Order. 
In quite young ovaries only two sorts of cells are seen — „Stock- 
cells” (Stammzellen), and egg cells in the earliest stage of development. 
In older ovaries, besides these two, there are seen the follicle cells 
lying between the eggs which are in various stages of development. 
The follicle cells arise from the Stammzellen like the egg cells, 
and as has been pointed out by various authors, are really only egg 
