64 bulletin: museum of comparative zoology. 



the testes were left in the fluid from one to two hours. All the material, 

 after being hardened a few days in alcohol was imbedded in paraffin 

 and kept in that condition until sectioned. Sections were cut from 

 three to ten micra thick. -A number of staining methods were tried, 

 but it was soon found that Heidenhain's iron hematoxylin preceded 

 by Bordeaux R, gave results which were much superior to any other 

 method, and in the later part of the work this stain was used almost 

 exclusively. In using this method the best results were obtained by 

 staining in a 1% aqueous solution of Bordeaux for twenty-four hours, 

 then transferring to the ferric alum for from one to two hours, after 

 which the sections were placed in hematoxylin for from four to six 

 hours. It is necessary to dehydrate very rapidly, as the Bordeaux is 

 quickly extracted by the alcohol, but with a little care the desired in- 

 tensity of the cytoplasmic stain can be obtained. Hermann's safra- 

 nin- gentian combination was used in some cases, but was found to 

 be unreliable as a differential stain for the monosome, as I shall call 

 the accessory chromosome. 



Most of the terms employed are those in common use among cytol- 

 ogists, and so require no explanation, but for the sake of clearness 

 and simplicity it has seemed best to adopt in the case of the chromo- 

 somes the nomenclature proposed by Montgomery (:06) as follows: 

 Chromosome, the word introduced by Waldeyer, to be used as a general 

 term for each separate mass of chromatin and linin which appears in 

 the cell during mitosis. Autosomes, the non- aberrant chromosomes. 

 Allosome,' any chromosome which behaves differently from the auto- 

 somes. Two kinds of allosomes are distinguished as follows: 



(1) Monosome. Allosomes which are unpaired in the spermatogonium. 



These chromosomes have been called variously, accessory chro- 

 mosomes (McClung), chromosomes speciaux (de Sinety), hetero- 

 tropic chromosomes (Wilson), etc. 



(2) Diplosome. Allosomes which are paired in the spermatogonia. 

 These have been called chromatin nucleoli (Montgomery), idio- 

 chromosomes and m-chromosomes (Wilson), and heterochromo- 

 somes (Stevens). 



III. Observations. 



1. Structure of the Testis. 



The following description of the testis, although based primarily 

 on Dissosteira Carolina, will apply equally for all the iVcrididae, since 

 the structure is essentially the same throughout the family. 



