300 KANSAS UNIVERSITY SCIENCE BULLETIN. 



ZU(ir.OGICAL LABORATORY. 



Nowlin ('08, just being published) for Melanoplus, one of the 

 Acridiinse, and Montgomery ('05) Syrbula acuticoymis, one 

 of the Truxalinse. Whether there is anything of particular 

 significance in the fact or not will of course appear later on. 

 The presence, however, of this grouping in every cell is again 

 evidence of the individuality of the chromosomes, for it is a 

 certainty that the members of these two groups are entirely 

 distinct and different individuals. There is no danger of ever 

 confusing any such large chromosomes as Nos. 12, 11 or 10 

 with any so small as Nos. 3, 2 or 1. The same might be said 

 of any of the intermediate members of the series, those which 

 approach each other more nearly in size, were we able to dis- 

 tinguish between them by their sizes. But the proof afforded 

 by the extreme members of the complex is enough to establish 

 individuality for all. 



Shape or form among chromosomes, as mentioned above, 

 does not seem to be a matter of first importance but is de- 

 pendent in a measure upon size. It is true that some chro- 

 mosomes, as Nos. 12 and 11 or 9, were found to be always 

 rings throughout the twenty-five cells that were studied, but 

 again No. 10 was found to have two out of the twenty-five 

 that were not rings, and possibly if we had searched far enough 

 the 12's, ll's and 9's would have shown similar variations. 

 Yet the two No. lO's that did not form rings were in all prob- 

 ability as truly No. 10 chromosomes as any other No. lO's in 

 the column, for No. 10 in series 5 or 6 bears the same size 

 relation to its fellows in the series as do any of the ring-form 

 No. lO's to their fellows. It is not essential that No. 10 be a 

 ring, but it is essential that the limbs of 10 be long and that 

 it contain the same amount and the same kind of material 

 that all other No. 10 chromosomes contain. The fact that the 

 limbs of this chromosome are long and slender makes it more 

 possible for it to form a ring, since the limbs have a better 

 chance to bend around toward each other. This possibly 

 might in a general way account for the fact that more rings 

 are found among large chromosomes than among small. 

 The latter, however, is not always true, for chromosome No. 

 4, which is very small, maj^ often be a ring, while No. 8, a 

 much larger chromosome, is never a ring. Possibly the thick- 

 ness and corresponding shortness of the limbs of the No. 8's 

 may be the reason why they never form rings. Nos. 7 and 4 



