482 THE POPULAR SCIENCE MONTHLY. 



pected, we here find that agamogenesis may go on without end. 

 Numerous plants and trees are propagated to an unlimited extent 

 by cuttings and buds ; and we have sundry plants which can not 

 be otherwise propagated. The most familiar are the double roses 

 of our gardens : these do not seed, and yet have been distributed 

 everywhere by grafts and buds. Hothouses furnish many cases, 

 as I learn from an authority second to none. Of " the whole host 

 of tropical orchids, for instance, not one per cent has ever seeded, 

 and some have been a century under cultivation." Again, we have 

 the Acorus calamus, " that has hardly been known to seed any- 

 where, though it is found wild all over the north temperate hemi- 

 sphere." And then there is the conspicuous and conclusive case 

 of Eloidea Canadensis (alias Anacharis) introduced no one knows 

 how (probably with timber), and first observed in 1847, in several 

 places ; and which, having since spread over nearly all England, 

 now everywhere infests ponds, canals, and small slow rivers. The 

 plant is dioecious, and only the female exists here. Beyond all 

 question, therefore, this vast progeny of the first slip or fragment 

 introduced, now sufficient to cover many square miles were it put 

 together, is constituted entirely of somatic cells; and this cell- 

 multiplication, and consequent plant-growth, show no signs of de- 

 crease. Hence, as far as we can judge, these somatic cells are 

 immortal in the sense given to the word by Prof. Weismann ; and 

 the evidence that they are so is immeasurably stronger than the 

 evidence which leads him to assert immortality for the fissipa- 

 rously-multiplying Protozoa. This endless multiplication of so- 

 matic cells has been going on under the eyes of numerous ob- 

 servers for forty odd years. What observer has watched for forty 

 years to see whether the fissiparous multiplication of Protozoa 

 does not cease ? What observer has watched for one year, or one 

 month, or one week ? 



Even were not Prof. Weismann's theory disposed of by this 

 evidence, it might be disposed of by a critical examination of his 

 own evidence, using his own tests. Clearly, if we are to measure 

 relative mortalities, we must assume the conditions the same and 

 must use the same measure. Let us do this with some appropriate 

 animal — say Man, as the most open to observation. The mortality 

 of the somatic cells constituting the mass of the human body is, 

 according to Prof. Weismann, shown by the decline and final ces- 

 sation of cell-multiplication in its various organs. Suppose we 

 apply this test to all the organs : not to those only in which there 

 continually arise bile-cells, epithelium-cells, etc., but to those also 

 in which there arise reproductive cells. What do we find ? That 

 the multiplication of these last comes to an end long before the 

 multiplication of the first. In a healthy woman, the cells which 

 constitute the various active tissues of the body continue to grow 



