5o6 The Ohio Naturalist. [Vol. IX, No. 7, 



CHROMOSOME DIFFERENCE IN ASCARIS 

 MEGALOCEPHALA.* 



John H. Schaffner. 



While studying at the University of Ziirich, in the winter of 

 1907-8, I spent some time working over a number of my old 

 Ascaris slides in order to compare the peculiarities of the chro- 

 mosomes with those of Agave virginica. The developing eggs 

 showed the four chromosomes to consist of two sizes easily dis- 

 tinguishable and a number of drawings were made at the time. 

 The work on Agave and other plants, however, prevented me 

 from following the matter further. In the meantime Mont- 

 gomery' has published a paper showing the same results as my 

 own observations. I wish, therefore, to present this con- 

 firmatory note on his very interesting report. 



I found that in the first two cleavage divisions, the chromo- 

 somes appeared as two longer and two shorter bodies. Mont- 

 gomery^ had previously (in 1904) concluded that the chromo- 

 somes of the polar spindles as well as of the first cleavage showed 

 a difiference in size, that the egg furnished one larger and one 

 smaller chromosome, that the sperm cell also contained one 

 larger and one smaller chromosome, and that the pairs can be 

 distinguished in the first cleavage. Griggs^ has also shown that 

 there is a difference in the shape and behavior of the two loops on 

 the reduction spindle of the egg. (Note his figures 5, 6, 7, 9, 10 

 and 11, which were however, not ver}^ satisfactority reproduced 

 in the printed paper.) 



My drawings were taken at random, and in some representing 

 older stages the difference is not so marked. The difference is 

 best seen shortly after the segmentation of the spirem, before the 

 extreme contraction has taken place. The difference in length 

 and shape is plainly shown in figures 1, 2, 3, 5 and 7. The 

 drawings are, of course, projections and the real difference is 

 shown to a greater or lesser extent depending on the angle from 

 'which the chromosomes are seen. Figure 1 is a spirem of the 

 second cleavage and shows the relative positions of the two 

 longer and the two shorter chromosomes. The spirem has just 

 broken at one point while two other constrictions are visible. 



* Contributions from the Botanical Laboratory of the Ohio Stale 

 University, XLIV. 



1. MoNTGOMKRy, Jr., Tho.m.\s H. On Morphological Difference of 

 the Chromosomes of Ascaris megalocephala. Archiv fiir Zellforschung, 

 Bd. 2, Heft, 1, p]). 66-7ri. 1908. 



2. Mo.N'TGoMiJRY, Jr., T. H. vSomc Ob.servations and Considerations 

 upon the Maturation Phenomena of the Germ Cells. Biological Bull. ().i;^7. 



3. Griggs. Robert F. A Reducing Division in Ascaris. Ohio 

 Nat. 6.- 519-527. 1906. 



