M'CLUNG : SPERMATOCYTE DIVISION'S OF THE ACRIDID.E. 85 



as a large and striking element of the mitoses of these cell generations 

 some time before the transformation into spermatocytes. Just when 

 it arises, or how, is not known. It appears tirst in the resting stage 

 of the spermatogonia, and from this time on throughout its whole his- 

 tory it manifests a steady and constant character. In relative size it 

 is always much larger than the other chromosomes, and in staining, it 

 maintains a constancy in striking contrast to them. Its part in the 

 formation of the spermatozoon is conspicuous and apparently impor- 

 tant. 



In the Acrididae, the uniformity of staining power and the periph- 

 eral position in the nucleus are maintained by the accessory chromo- 

 some, but its origin and relative size apj^ear to be diiferent. Instead 

 of appearing during a resting period among the ditfused chromatin, 

 it is at first observed as one of the sperm atogonial chromosomes per- 

 sisting in the nucleus, while its fellows break down into a granular 

 mass of chromatin. 



Appearing thus in the last series of spermatogonia, it does not ex- 

 hibit in its peculiar character until the spermatocytes are established. 

 Fig. 4 shows the first stage, so far observed, in the production of the 

 accessory chromosome in Hippiscus. Throughout the prophases of 

 the first spermatocyte, it is to be noted as a strongly staining, sharply 

 outlined body, lying directly under the nuclear membrane. In this 

 character and position it persists until it takes its place in the meta- 

 phase ready for division. Here it is so much like the rest of the 

 chromosomes that it is impossible to distinguish it from the others. 

 There is, therefore, every reason to believe that it comports itself 

 through the division like its fellow chromosomes. A discussion of 

 its position and character in the spermatid will be reserved for a sub- 

 sequent paper. 



The alluring explanation by Paulmier concerning the function of 

 the accessory chromosome unfortunately receives no supijort in the 

 behavior of this structure in the Orthopteran testis. If extreme 

 constancy in form, structure and staining reaction is any indication 

 of permanency and importance, then no other cell element excels 

 this one in the possession of these qualities. Every ob.servation made 

 upon members of the Acrididse, as well as of the Locustidjc, tends to 

 support the view that the accessory chromosome is of primary im- 

 jortance in the development of the spermatozoon. It is almost in- 

 variably the case that when a part is in the progress of degeneration 

 t becomes extremely variable and eccentric in its behavior, During 

 dl the divisions in which it takes part, the accessory chromosome pur- 

 ues a uniform course, witli the apparent purpose of carrying its sub- 

 ;tance through to the end of the process with the least possible in- 



