64 ETHEL NICHOLSON BROWNE 



The only difficulty with my material has been the scarcity of 

 spermatogonia! divisions and early growth stages. 



The testes are bifurcated coiled tubes lying on either side of 

 the alimentary canal. They were dissected out in Ringer's 

 solution and transferred at once to the fixing fluid. Flemming's 

 strong fluid, Bouin, Carnoy, Gilson and corrosive sublimate were 

 used with results that are favorable in the order named. Heiden- 

 hain's haematoxylin was used almost exclusively as a stain, though 

 some saffranin preparations were made. In order to demon- 

 strate mitochondria, some of the testes were fixed with Benda's 

 modification of Flemming's fluid, and these were subsequently 

 treated with his mitochondrial stain of sulphuralizarinate of 

 sodium and crystal violet, used according to his original method. 

 The results of the fixed preparations have been controlled by 

 observations of the living cells both with and without intra-vitam 

 stains. By dragging the testis over a slide and mounting in a 

 drop of Ringer's solution, very good results were obtained. 

 The mitochondria and karyosphere may at once very clearly be 

 seen; and after half an hour or so, the chromosomes in division 

 stages come out very clearly. This is probably due to the fact 

 that some change has taken place in the chromosomes, and it 

 may be that they are not visible in the living state. Such would 

 seem to be the case from the fact that constant observation of 

 anaphase spindles failed to reveal any progression of the chromo- 

 somes toward the poles. In some cases it was possible to count 

 the chromosomes in these preparations. 



III. CHROMOSOMES 



A. Observations 



As pointed out in my preliminary paper ('10), the study of 

 the chromosomes in Notonecta has proved of much interest from 

 the fact that the change in number from species to species can 

 here be attributed to the relations of a particular chromosome. 

 Briefly the results are as follows. In all three species there is 

 present an unequal Xl^-pair of chromosomes which divide sepa- 

 rately in the first spermatocyte division but are united in the 



