(U2 APPENDIX B. 



where bathes the outer surface : the utilization of its contained 

 material being effected gratis by the Sun's rays. Just as was to 

 be expected, 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 

 cannot 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 culti- 

 vation." Again, we have the Acorus calamus, " that has hardly 

 been known to seed anywhere, though it is found wild all over 

 the north temperate hemisphere." And then there is the con- 

 spicuous and conclusive case of Eloidea Canadensis (alias An- 

 acharis,) 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 slow rivers. The plant is dio?cious, and only 

 the female exists here. Beyond all question, therefore, this vast 

 progeny of the first slip or fragment introduced, sufficient to 

 cover many square miles were it put together, is constituted 

 entirely of somatic cells. Hence, as far as we can judge, these 

 somatic cells are immortal in the sense given to the word by 

 Professor Weismann ; and the evidence that they are so is im- 

 measurably stronger than the evidence which leads him to assert 

 immortality for the fissiparously-multiplying Protozoa. This 

 endless multiplication of somatic cells has been going on under 

 the eyes of numerous observers for forty odd years. What 

 observer has watched for forty years to see whether the fissi- 

 parous multiplication of Protozoa does not cease ? What ob- 

 server has watched for one year, or one month, or one week ? * 



Even were not Professor 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 



* Respecting the Elmdei I learn that in 1879 thirty years after it had 

 become a pest one solitary male plant was found in a pond near Edin- 

 burgh ; but " in an exhaustive inquiry on the plant made by Dr. Greenland, 

 of Copenhagen, he could find no trace of any male specimens having been 

 found in Europe other than the Scotch." In waters from which the 

 Eloidea has disappeared, it seems to have done so in consequence of the 

 growth of an Alga, which has produced turbid water unfavourable to it. 

 That is to say, the decreased multiplication of somatic cells in some cases, 

 is not due to any exhaustion, but is caused by the rise of enemies or 

 adverse conditions; as happens generally with introduced species of plants 

 and animals which multiply at first enormously, and then, without any loss of 

 reproductive power, begin to decrease under the antagonizing influences which 

 grow up. 



