180 KEPOKT— 1891. 



between these two extremes there are to be found a continuous 

 series of intermediate gradations. 



Moreover, cases analogous to those of Begonia and other 

 plants already referred to are to be met with also among 

 animals. It is a well-known fact that in many animals, and 

 in not a few that belong not to the lower but to the higher 

 types, there is the powder of regeneration of a lost limb, or tail, 

 or even head. The limbs or tail of some salamanders, for in- 

 stance, ^Yill if removed be replaced by perfect organs developed 

 by a process of budding, and the same holds good of many 

 Arthropods and Molluscs. - These phenomena are met by 

 Weismann with the admission that in such cases a certain 

 amount of germ-plasm may be preserved unaltered in the 

 somatic cells. It is, in fact it would now appear, only in the 

 highest forms that the germinal matter is all concentrated in 

 the germ-cells. But it is clear that Weismann's whole argu- 

 ment rests on the postulate that from the beginning of meta- 

 zoan and metaphytal life the germ-plasma has remained apart 

 from the other protoplasmic elements of the body — so isolated 

 in fact as not to be affected (except, as afterwards admitted, 

 in the case of the ova themselves) by any of the influences 

 affecting the organism as a whole. And, it has already been 

 pointed out, many of the cases in which it is necessary to 

 suppose the presence of germ-plasin in the somatic cells are by 

 no means cases of lowly-organized animals and plants. 



But, it might be urged, though to explain these cases it is 

 necessary to suppose the jDresence of germinal matter in a 

 larger or smaller number of somatic cells, this germinal matter 

 is not in the direct line of descent from ovum to ovum ; it has 

 been detached from the main mass of the germinal material 

 and passed to the various parts of the body in order to provide 

 for the possibility of mutilation, or to provide a ready means of 

 multiplication. But such an explanation will not bear a close 

 scrutiny. 



In the case of Begonia, it is only necessary to point out that 

 complete ova are afterw^ards developed on plants propagated by 

 leaves, and that the germinal substance of these ova can only 

 have been derived from tlie j)articles of germinal matter 

 scattered through the cells of the leaves. And in animals of 

 tolerably high organization the same holds good. Thus regene- 

 rated Chsetopods develope anew the reproductive elements. 

 But the most cogent examples in the animal kingdom of the 

 formation of ova from material in somatic cells are afforded by 

 the phenomena of budding and regeneration in the Bryozoa" 

 and the colonial Tunicata. 



* ]'ide Seeliger : " Bemerkmigen ziu- Knospeubildung dcr Bryozoen," 

 '' Zeitschr. f. wiss. Zool.," v. Bd. (1890). 



