I. Methods.
While other fixing agents were used, Flemming’s chromo-acetic-osmic mixture (strong) proved the best. Its fixation was satisfactory in all but a few stages, where the chemical changes going on in the cell are such that it seems difficult, probably impossible, to secure good, clear results; at least, neither Gilson’s nor Zenker’s mixture did any better on cells in these stages.
Heidenhain’s iron-hæmatoxylin stain gave the best results, although Flemming’s three-color method was very satisfactory.
Most of the observations are made from sectioned material, but smear preparations were used for advanced spermatozoa.