A Comparative Study of tlie Chromosomes etc. 
247 
Amphiscepa hivittata (Say), and I shall at times refcr to certain fcatures 
in the sperniatogenesis of these Homoptera in Connection with E. curvata 
and E. binotata. The testes and ovaries were dissected, under a dissecting 
microscope, from the living insects in physiological salt solution and 
immediately transferred to the fixing fluid. For the testes and young 
ovaries, Hermann’s fluid, Flemming’s fluid (strong) and Bouin’s fluid 
were principally employed. Hermann’ s fluid gave the best fixation, 
the clearest figures and the finest cytoplasmic preservation. It has less 
tendency than Flemming’s fluid to increase the contraction at synizesis. 
Flemming’s fluid was used according to the method employed by Meves 
und Duesberg (’08), viz. treated, after fixation, with pyroligneous acid 
and chromic acid and stained in crystal violet and alizarin. Bouin’s 
fluid makes the chromosomes appear sharply defined, but is not satis- 
factory for studying the growth period in spermatogenesis. Wlienever 
possible, the material w^as immediately embedded. The Chloroform 
method, with evaporation at low temperature, was employed and sections 
were cut five micra in thickness. Heideniiain’s haematoxylin, with 
Bordeaux red or Congo red as counterstains, was found to be the best 
method of staining. Crystal violet and alizarin, although failing to establish 
the presence of a definite mitochondrial mass, gave most excellent figures 
for the study of the growth period, and differentiated the “X-element” 
well. Safranin and Lichtgrün, Flemming’s triple stain, gentian-violet 
and thionin were also used on sections of testes in both species. 
Smear preparations were made by crushing the testis and spreading 
its substance as evenly and quickly as possible over the surface of the 
slide, and then inverting the still moist surface over a dish of w’arm 
Flemming’s fluid. The vapor of the fluid immediately Condensed on 
the surface of the preparation and generally prevented its drying, although 
at times the edges did dry. The smears, after exposure to the fumes 
for about five minutes, Avcre washed in running water and then stained 
in Heideniiain’s haematoxylin. 
Testes crushed in physiological salt solution containing a small 
amount of neutral red were examined in the fresh condition. They 
showed the chromosomes and spindles, which corresponded w’ell wdth 
those of the fixed material. 
IV. Systematic Relation of the Insects. 
In making a comparison of the chromosomes of two nearly related 
animals, it is well to know, as far as possible, their exact systematic relation. 
