308 J. BS,’ MOORE: 
at one end to the spindle surface, the two halves gradually 
separating in the manner represented at 2,d,e. Quite recently, 
however, Farmer showed! that in the division of the pollen 
mother-cells of Lilium candidum this description of the 
origin of the daughter-chromosomes by no means fits the 
facts. After arising as long closed loops of microsomes, the 
chromosomes assume the rod form previously known ; but the 
apparently longitudinal splitting extends only part of the way 
towards the outer end. When they have become flattened 
out on the spindle surface—sometimes before, and always as 
soon as the transverse fission is apparent (Diagram IV, 3, d.)— 
there is seen another longitudinal split, which converts the 
chromosomes into a closed loop, exactly comparable to those 
of the animals I have just described (1V, 1), the four masses 
into which the equatorial thickenings are divided at the time 
of separation being very marked (IV, 3, d, ¢.). 
57. Professor Farmer has kindly given me photographs of 
these details, which I have copied in Diagram IV, 3. It 
therefore appears extremely probable that the chromosomes 
described by Guignard and Strasburger are, in reality, like 
those of Lilium candidum, closed loops bent upon them- 
selves, but that the great shortening up and thickening they 
undergo leads here, as it often does in animals, to the internal 
opening being difficult to see. 
58. The outcome of all this is that the reproductive cycles of 
animals and plants correspond, not only in the number of the 
chromosomes typical of the somatic cells of any species being 
halved, but also in the successive and complex phases by which 
their numerical reduction is brought about, as well as in the 
type of modification which the post-synaptic cellular genera- 
tions may undergo. 
59. Now, with repect to the nature of these post-synaptic 
generations, it is made obvious by the fact that in Klasmobranchs 
there are two, while in mammals there appears to be only one, 
that their number is of no physiological importance in the 
! «Ueber Kerntheilung in Lilium-Antheren in Bezug auf die Centrosomen- 
Frage,” ‘Flora. Bot. Zeitung,’ 1895, Heft 1. 
