5°6 
The Ohio Naturalist. 
[Vo]. IX, No. 7, 
CHROMOSOME DIFFERENCE IN ASCARIS 
MEGALOCEPHALA.* 
John H. Schaffner. 
While studying at the University of Ziirieh, 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 * 1 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 2 had previously (in 1904) concluded that the chromo¬ 
somes of the polar spindles as well as of the first cleavage showed 
a difference 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 3 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 very satisfactorily 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 State 
University, XLIV. 
1. Montgomery, Jr., Thomas H. On Morphological Difference of 
the Chromosomes of Ascaris megalocephala. Arehiv fur Zellforschung, 
Bd. 2, Heft, 1, pp. 66-75. 1908. 
2. Montgomery, Jr., T. H. Some Observations and Considerations 
upon the Maturation Phenomena of the Germ Cells. Biological Bull. 6.137. 
3. Griggs. Robert F. A Reducing Division in Ascaris. Ohio 
Mat. 6: 519-527. 1906. 
