CHROMOSOME STUDIES IN THE DIPTERA 49 



usually lying radially in metaphase, i.e., one end pointing toward 

 the center, the other toward the margin of the plate (diagram 

 1 a, /i) ; attached to the spindle fiber at one end, and going to the 

 poles as elongate straight rods, {h, diagram 1 b, and fig. 6) ; con- 

 tracting precociously in prophase. 



3. The large autosomes. Two pairs (in Type I) ; very long, more 

 or less dumb-bell-shaped, with a definite constriction in the 

 middle {I, diagram, 1 a and fig. 5); usually V- or U-shaped in 

 metaphase, the apex of the V coinciding with the constriction 

 and pointing toward the center of the plate, thus bringing the 

 arms of the V into the position of radii pointing toward the mar- 

 gin; attached to the spindle fiber, not at one end, but at the 

 median, constricted part, and going to the poles in V-shape 

 {I, diagram 1 b and figs. 6 and 7) . 



The essential features in the behavior of these different sorts 

 of chromosomes are indicated in figures 1 to 7 and diagrams 1 a 

 and 1 b. Figure 7 shows an anaphase in polar view illustrating 

 the difference between the V-shaped, large autosomes and the 

 straight sex-chromosomes. Only one pole is figured, the other 

 being almost identical with it. In this figure the m-chromosomes 

 are not evident. Figure 6 shows the same features in side view. 

 It is taken from the second maturation division of the male, in- 

 volving only the haploid number of chromosomes (4), and 

 although one pole is somewhat confused the figure shows the 

 decided difference between the two kinds of chromosomes 

 {I and h) . 



are concerned, my observations are entirely in accord with hers. But in the matu- 

 ration divisions, where she describes a distinct X element separable from the Y of 

 which it was formerly an integral part, I fail to corroborate her statements. So 

 far as my observations go, they indicate an unequal XY pair in the male, without 

 any additional piece attached to either. Neither my observations nor those of 

 Miss Stevens are conclusive, however, owing to the difficulty of observing the 

 chromosomes in these stages. The question is important for the bearing it has 

 upon the breeding experiments with this fly, and we are doubly unfortunate in 

 being thus far unable to settle it. By a recent examination of males of another 

 species, having the same type of chromosomes as ampelophila, and showing more 

 favorable conditions for their study, I have been led to hope that through this 

 species some light can be thrown on ampelophila. 



