WILCOX : SPERMATOGENESIS. 5 



(2) after staining, (3) after decolorizing. Simple immersion in water 

 does not do as well. The mordant and stain will form a precipitate, 

 just as in Henneguy's method, and if the first washing be neglected, it 

 is next to impossible to remove the precipitate by subsequent washings. 

 One to five minutes in a stream of water is enough for each washing. 

 The sections will become quite opaque immediately after immersion in 

 the decolorizer, but in this the opacity is slowly removed. The decolori- 

 zation is hastened by washing the sections in water at intervals during 

 the process of decolorizing. This is necessary, also, in order to see how 

 far the decolorizing has progressed. The process can thus be stopped 

 at the desired stage. The proper decolorization is the most difficult 

 part of this method. 



By the " blue " process, so far as my experience goes, the cytoplasm 

 stains gray, the centrosomes do not stain at all, the spindle and linin 

 fibres very faintly, the chromosomes dark blue. By the ''black" pro- 

 cess the cytoplasm takes a dark-gray color, and both centrosomes and 

 chromosomes are made black, while spindle fibres and linin fibres be- 

 come very distinct. The nucleoli are colored nearly black by either 

 process. 



CICADA TIBICEN. 



The testes of Cicada tibicen are paired, and each consists of a large 

 number of ellipsoidal follicles, which are closely packed together. The 

 follicles of each side of the body open into a vas deferens, which soon 

 joins its fellow of the opposite side. Figure 14 (Plate I.) gives an idea 

 of the spatial relationship to one another of different sperniatogenetic 

 stages. It represents a very nearly longitudinal section of a follicle of 

 Cicada. At a are spermatogonia ; at d, spermatids in various stages of 

 metamorphosis. 



The Cicada material at my command did not show the division stages, 

 but it gave a very reliable series of preparations on certain other stages. 



The spermatogonia lie at the blind end of the follicle. They occupy 

 in my preparations only the single end-compartment (Fig. 14, a). Their 

 size is less than that of the spermatocytes, and they are further distin- 

 guished from them by the fact that they have only 12 chromatic rods, 

 whereas the spermatocytes have each 24 spherical chromosomes. One 

 or often two nucleoli are to be seen. 



The spermatocytes occupy usually two compartments next to that of 

 the spermatogonia. The chromatic substance consists of about 24 



