1*56 MONTGOMERY A STUDY OF THE CHROMOSOMES 



stronger solution), Hermann's chromo-aceto-platinic chloride mixture, and a picro-acetic 

 mixture recommended by Prof. Conklin (100 parts saturated aqueous solution of picric 

 acid, 100 parts distilled water, G parts glacial acetic acid) being used. Of these the 

 mixtures of Flemming and Hermann proved the best for the chromosomal structures, for 

 the picro-aSetic mixture, while giving an excellent preservation of the actromatic spindle 

 structures, swells the chromosomes very considerably so that on pole views of monaster 

 stages they generally appear closely apposed to one another, which makes it difficult to 

 count them. Where the species is small it is necessary to remove the testes in the fixa- 

 tive under a dissecting microscope. The sections were stained either by the iron-hsema- 

 toxylin method of Heidenhain or by the saffranine-gentian violet method of Hermann. 



II. OBSERVATIONS. 



PENTATOMID^E. 



1. Euchistm variolarius Pal. Beauv. 



This is the species the spermatogenesis of which I described under the name of 

 " Pentatoma " in a former paper (1898) ; twenty-eight testes were studied from adult 

 individuals of all seasons except the winter months. 



In my former paper (I. c.) I did not find chromatin nucleoli in the spermatogonia ; I 

 concluded that there was no stage of longitudinal splitting of the chromosomes during the 

 growth period, and I concluded that the second maturation division was a reduction 

 mitosis like the first. Shortly afterward appeared the papers by Paulmier (1898, 18!M>) 

 on the spermatogenesis of Anasa tristis, wherein he showed that there are two chromatin 

 nucleoli (his "small chromosomes") in the spermatogonia, and that these unite in the 

 spermatocytes to form one bivalent one ; that the chromosomes undergo a longitudinal 

 splitting in the growth period, and that the second maturation division is equational. In 

 those points wherein I differed from Paulmier, I find that Paulmier is correct, and that I 

 gave a wrong interpretation to the phenomena in Euchistus. I find nothing to correct in 

 the matter of the other points described in my earlier account, and here give briefly 

 merely the necessary emendations to my former paper. 



Spermatoyonia. In the resting spermatogonium there are in the nucleus beside the 

 true nucleolus (of which there may be more than one) two small chromatin nucleoli of 

 rounded form (Plate I, Fig. 1, N. 2). With the saffranine-gentian violet stein of Her- 

 mann, when properly used, these stain bright red, the true nucleolus a faint bluish, the 

 chromatin proper a deep violet ; careful staining and thin sections are necessary to show 

 them plainly. Sometimes one or both of them are attached to a true nucleolus. In the 

 prophases of mitosis the chromatin nucleoli are easily recognizable by being muct^ smaller 



