Beard, Heredity and the epicycle of the germ-cells. 323 



from the somatic cells. Probably all the higher plants, the Metaphyta, 

 are here referred to ; for in many of the lower plants all the cells 

 might be regarded as potentially reproductive, or ,,sexual". In the 

 higher plants the ,,sexual cells" do appear at a very early period i u 

 the sexual generation. The higher one ascends the earlier is this 

 epoch; for in the flowering plants, for instance, the life-span of the 

 sexual generation, the gametophyte, is exceedingly short, and it is 

 concerned solely with the differentiation of, and the provision for, the 

 sexual cells. These latter certainly do not appear as such in the 

 asexual generation or sporophyte, nor is it to be expected, that they 

 should. Were they to do so, the sporophyte would lose this character, 

 and become a gametophyte. Moreover, even in the asexual generation, 

 the sporophyte, the morphological continuity is unbroken, for in this 

 the future germ-cells are represented by their direct ancestors, the one 

 or more cells forming the apex 1 ). 



WhatNussbaum rightly insisted upon was, the early appearance 

 of the germ-cells in the sexual generation of animals, i. e., in the em- 



1) Compare Noll's eloquent testimony in the following: ,,The con- 

 tinuity of the embryonic substance. - The vital capacity of the cells 

 of the functioning permanent tissue is always limited in time, mostly, indeed, 

 very closely so. Without limit, on the contrary, and never finding a natural 

 close the vital power of the embryonic substance is preserved. This it is, 

 which forms the growing points of the perennial plants, and from this, as 

 Sachs first demonstrated, the growing points of the sexual progeny are di- 

 rectly derived through the substance of the germ-cells. This embryonic sub- 

 stance does not age, it produces new passing individuals, but it is permanently 

 preserved in their progeny : it is always productive, always growing young and 

 increasing. Thousands upon thousands of generations, which have arisen in 

 the course of millions of years, were its products, but it lives on in the youngest 

 generations with the power of giving origin to coming millions. The indi- 

 vidual organism is transient, but its embryonic substance, which produces 

 the mortal tissues, preserves itself imperishable, everlasting, and constant. 

 Regarded from this standpoint, the differences in the duration of life between 

 short and long-lived plants, between annual herbs and the thousands of years 

 old giants of the plant-race appear in another light. Out of the embryonic 

 substance of that lime tree of Neustadt every year new leaves and buds form, 

 but these remain in connection with the dying remains of structures of earlier 

 years. In the annual plant, on the contrary, the embryonic substance sepa- 

 rates itself every year in the embryo from the mortal remains, and forming 

 new branches, leaves, and roots, becomes a completely new individual. 



At the basis of the old and well-known dictum of Harvey, omne vivum ex 

 ovo' there thus already lay the continuity of the embryonic substance. This 

 is, at the same time, in eternal youth and organic immortality the substance 

 of the unicellular organisms, which reproducing by fission, are used up in one 

 another without residue." 



F.Noll, in Strasbu rger's Lehrbuch der Botanik, zweite Auflage, 1895, 

 p. 208209. 



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