A8 MR. C. F. U. MEEK ON 
estimated from the magnification, is 8 uw in each cell, and this 
confirms my original measurement; for the length was said 
to be 7°8 x during constriction and 8-1 » at the moment when 
constriction was complete. 
Fig. 13 is a polar view of the primary spermatocyte complex, 
and all the chromosomes are shown. Fig. 14 is a lateral view at 
the conclusion of the metaphase; the chromosomes have com- 
pleted constriction, and the daughter rods are ready to move 
towards the two poles. This photograph has been made at a 
magnification greater by s'-th than that of the remaining figures. 
In my earlier paper the length at this stage was said to be 
10-4 »; and, since the length, estimated from the photograph, 
is 10°5 p, my original measurement is seen to have been accurate. 
There is, however, a new factor that must be considered in the 
case of this organism. J remarked in my paper that, at the 
conclusion of the primary spermatocyte metaphase, certain cells 
showed a spindle-length greater than that required by the ratio. 
Such spindles seemed to be distorted, and, after careful con- 
sideration, I assumed that they were abnormal in that their 
true form had been destroyed in the process of section-cutting. 
T have recently studied new preparations of this material, and 
have again found spindles of excessive lengths. These occur 
in cells that are closely packed together ; but, since many of the 
spindles show no sign of distortion, we are not justified in 
assuming abnormality in every case. 
Four explanations can be put forward. First, the volume of 
these cells in the metaphase may vary, and our proposition may 
still be valid. In this case, however, various lengths will pre- 
sumably be found at the conclusion of the secondary spermatocyte 
metaphase; and I have not observed such lengths. Secondly, 
the daughter chromosomes may remain apposed to one another 
in the equatorial plane for a considerable time after constriction 
is complete: if centrosome divergence continues during this 
period, the various and excessive lengths may be explained. 
This, however, cannot always occur; for, in this organism, 
I have found and drawn primary spermatocyte cells in which 
the daughter chromosomes have begun to move towards the 
poles when the spindle-length is only slightly greater than that 
estimated for the conclusion of the metaphase. Thirdly, our 
proposition may require modification in that the length of the 
spindle may be affected by the shape of the cell. My original 
measurements in orficula and Helix were made from cells that 
were approximately spherical, and this may explain the constant 
lengths observed. When, however, cells are closely packed 
together in a cyst, the spherical form disappears, and, if our 
modification is valid, the spindle-length will vary with the shape 
assumed. Lastly, the length of the spindle at this stage may be 
connected with neither the volume nor shape of the cell; and, 
in this case, our proposition is entirely disproved. If, however, 
