3i8
��THE SCIENTIFIC MONTHLY
��products act as poisons to other organisms or they may play an im- portant part in the vital activities of the organism itself^ as in the phosphorescence of NoctHuca, or as in reproduction and regeneratioD. Since regrowth or regeneration^® takes place in artificially separated fragments of cells in which the nuclear substance (chromatin) is be- lieved to be absent^ the formation of new parts may be due to a specific enzyme, or perhaps to some chemical body analogous to hormones and formed as a result of mutual interaction of the nucleus and the proto- plasm. Reproduction through cell-division is also interpreted theo- retically as due to action set up by enzymes or other chemical bodies produced as a result of interaction of nucleus and cell body. The
���INCC
��MOBOaCOailAFMT. lATC LOWUI CMIWMN (WAUOOMN OM OLWfUOB TIMt
X M**"" WWW* .»* ocnvi voixowoti m 9ean*m j^ mouhTj
��Fia. 1. The World in Late Lowbb Cambrian (Waucobian ob Olenellus) Timi.
After Schuchert.
��protoplasm is regenerated, including both the nuclei and the cell plasm, by the distribution of large quantities of nucleo-proteins, the specific chemical substance of chromatin.
Through this modern chemical interpretation of the Protozoan life cycle we may conceive how the three laws of thermod^Tiamics may be applied to single-celled organisms, and especially our fundamental bio- logic law of action, reaction and interaction. By far the most difficult problem in biologic evolution is the working of this law among the many-celled organisms (Metazoa) including both invertebrates and vertebrates.
During the long period of pre-Cambrian time, which is estimated at not less than thirty million years from the actual thickness of the
18 Op. cit., pp. 261-264, 266.
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