Reduction in Animals and Plants. 439 
contraction. Moreover it can be distinctly seen in the case 
of some animals while the cells are still alive. 
(3) That the division which closes the synaptic rest in lilies, 
being a true heterotype, like that in Tritons, the nuclear 
chromatine, during the chromosome-formation, pursues a course 
of evolution essentially similar in both. 
(4) That there are certain specific types of variation in the 
formation of the chromosomes, which repeat themselves with 
curious exactitude in both the animals and plants which we 
examined. 
Now these last points of correspondence in the variations 
the chromosomes may undergo, are in reality by far the most 
important observations we have made, because they show that 
the heterotype divisions of animals and plants correspond not 
only in the gross, but in the most minute details. They 
constitute, in fact, a series of phenomena from which it is 
legitimate to conclude that the heterotype mitoses in the 
reproductive cycles of animals and plants are intimately 
related to each other. They must arise in these reproductive 
cycles, either as the expression of identical physiological con- 
ditions, or be representative of a common ancestral stage in 
the phylogenetic history of both. 
In either case, these phenomena are of the most profound im- 
portance to the zoologist and botanist alike as the universal 
existence of the ‘ Reductionstheilung ’ does not, as we have 
seen, appear to be supported by the facts as at present known, 
its retention as a theoretical necessity can only continue to 
obscure the essential similarity which really exists between 
the reproductive cell-cycles of animals and plants. 
