SPERMATOGENESIS OF THE RABBIT. 295 



aqueous picric acid with fifteen parts formalin and ten parts 

 glacial acetic acid, were added one and one-half grams chromic 

 acid and three grams of urea. The solution was then heated to 

 thirty-seven degrees and the tissue added. This fixative made 

 the chromosomes stand out somewhat better and clearer than 

 any of the other fluids. 



The sections were cut from four to fifteen micra in thickness 

 and stained in (i) Delafield's haematoxylin and eosin, (2) Haiden- 

 hain's iron-haematoxylin and acid fuchsin or orange G, (3) 

 safranin with gentian violet or lichtgrun. Method (2) proved to 

 be the most successful and gave some very excellent results. 

 This method was most valuable in bringing out the detailed 

 structures, especially the chromatoid body. Cytoplasmic struc- 

 tures were as a rule satisfactorily stained in Flemming's triple 

 stain. 



Smear preparations were also made. These were fixed in 

 Flemming's strong or in Bouin's fluid. Haidenhain's iron- 

 hsematoxylin gave the most satisfactory result when counter- 

 stained with lichtgrun. 



Mammalian spermatogenesis seems to offer greater difficulties 

 for study than any other form. This is due to the impossibility 

 of securing by means of existing reagents and methods proper 

 fixation. In nearly all preparations it has been found that the 

 chromatic structures have a tendency to mass so that individual 

 details are lost. The chromosomes in the rabbit have this to a 

 very marked degree. The various stages in spermatogenesis 

 were numerous enough, but a great many stages had to be 

 examined in order to find those in which chromosome counts 

 were possible. 



N. M. Stevens (1911) in the spermatogenesis of the guinea- 

 pig found that material "very unfavorable and the results are 

 not so satisfactory as are desired." Montgomery (1912) in his 

 work with the human spermatogenesis has to say practically 

 the same thing, "the fixation was not as excellent as might be 

 desired." Wodsedalek (1913), however, seems to have encoun- 

 tered less of the massing of chromosomes in the spermatogenesis 

 of the pig than is present in other mammalian forms. 



In both the rat and the guinea-pig, and later in the bull, the 



