M'cLUNG : SPERMATOCYTE DIVISIONS OF THE AC'RIDID.E. 77 



gomery,in his late paper upon the spermatogenesis of Pentatoma (8), 

 commences his consideration of the spermatocytes with the anaphases 

 of the spermatogonia. To the treatment of this part of the subject 

 by Montgomery I shall have occasion to refer later. 



It will be noticed that I make no reference to the so-called "synap- 

 sis" stage. It is thus slighted because I have good reasons to regard 

 it merely as an accident in the process of preparation and not as a 

 normal condition of the nuclear elements. At least such is the case 

 in the testicular cells of the Orthoptera. 



As stated in a previous paper (23), I agree with Montgomery that 

 the designation "chromosome" should not be applied indiscriminately 

 to all chromatic elements that occur in the cell. It is obviously very 

 confusing to have one author denominate a tetrad a chromosome, and 

 to have another apply the same term to each of the elements compos- 

 ing the aggregate. According to the above-mentioned author, the 

 chromosome is a unit prepared for separation in the equatorial plate, 

 and it is to units occupying this position in the cell that the term 

 should be applied, regardless of what they have been or what they are 

 to become. I am much in sympathy with the endeavor to have the 

 term "chromosome" apply to but one clearly defined cell element. 



Since, however, the chromosomes are bodies designed to be sepa- 

 rated by metakinesis, which do not acquire their full development 

 until the metaphase is reached, I do not hold their origin in the 

 prophases so essential in their determination as does Montgomery. 

 This would be a matter of little moment were it not for the accessory 

 chromosome that occurs in insect reproductive cells. This element, 

 which I consider as much a chromosome as any of the others that come 

 t(j lie in the equatorial plate, never loses its identity in the prophases 

 as do the others, and so cannot be traced back to an origin from the 

 s[)ireme of that cell, as becomes necessary according to Montgomery's 

 definition. 



While subscribing, therefore, to the definition proposed by tliis in- 

 \ tstigator, in so far as it concerns the unity of the element in ques- 

 tion, I differ from him with regard to the importance that must be 

 attached to the preliminary stages of the formation. It is, of course. 

 iiiil)OSsible to make a definition that will stand accurately for all cases. 

 •specially where the knowledge is so scant as it is in the present in- 

 stfince, but for convenience of description it is almost necessary to 

 linve some definite statement regarding the views of a writer. I shall. 

 oil that account, endeavor to state in a few mords my conception of a 

 ■chromosome, having in mind the points made by Henking and Mont- 

 LToiuery regarding the present value of the element, without question- 

 ing its past or prospective relationships. 



These considerations would lead me to frame a definition some- 



