1226 General Notes. [December, 
to influence heredity must affect this structure and thus only, can 
produce variation. 
We have finally to inquire, what are the changes which the 
idioplasm suffers during the ontogenetic development of an or- 
ganism ? Lach cell which results from the segmentation of the first 
embryo nucleus must be the equivalent, in all respects, of this nucleus, 
and, theoretically, capable of reproducing the individual. Weis- 
mann has a theory opposed to this view. According to this 
author, only the very earliest cells produced in segmentation are 
set apart as germinal cells; all others have lost the power to be 
germinal cells, but must invariably differentiate into the organs 
of the body. Thus we really have no death, but only a series of 
germinal cells which gives off, by cell multiplication, from the 
fertilized egg, a mass of cells which differentiates into the indi- 
vidual. This aggregate alone is dissolved in the process known 
as death. 
Kölliker cannot accept this theory. Every organ begins in a 
mass of embryonic cells, from which parts may be renewed if lost. 
Cells that have differentiated may, under proper circumstances, 
regain their germinal power. The buds that appear at various 
points of a mass of embryonic vegetable tissue, essentially repro- 
duce the structure of the individual. In plants, the germinal 
cells can not be said to be set apart early in life. (Compare also 
adventitious buds.) Even in the adult animal organism, occur 
embryonic cells, such as osteoblasts and odontoblasts, the deep 
cells of the epidermis, cells of many glands, lymph, cells, and 
germinal cells. The last are themselves, like other cells, differ- 
entiated in a particular direction, some forming eggs and some 
spermatozoa. All asexual reproduction, such as fission, budding, 
parthenogenesis, shows that other cells besides germinal cells, can 
reproduce the organism. It would be an interesting inquiry to 
ascertain what circumstances cause the cells to reproduce the 
whole body or only a part. It is not necessary to hold the early 
differentiation of germinal cells, nor to locate them for all animals 
in the same embryonic layer, since all cells are primarily germi- 
nal cells like the fertilized egg; and according to the function 
they are to serve in the adult, they differentiate into the appro- 
priate tissues.— F. Nelson. 
Tue RETROGRADE METAMORPHOSIS OF SIREN.—I have already 
_ pointed out (NATURALIST, 1885, p. 245) that palaontology shows 
oS _ that the Batrachian order of Trachystomata, which embraces the 
ount for the curious condition which 
rved in the branchiz of the Sirens. The 
