Aug., 1890. 
weismann ! s theory of germ-plasm. 
177 
it here, as it fails to express one or two matters that I think 
should be shown, and which are likely to give rise to dispute. 
I will refer to this later. 
Commencing with the fertilised ovum, we see it presently 
divided into two cells, one of which (according to the theory) 
is set apart for the purposes of reproduction. Now Weismann 
supposes that this division is a division of the cell into two 
equal halves as regards quantity, but unequal in quality ; 
that one of the parts retains a greater share of a certain 
property than the other. One of these further divides to 
form the body or Soma, while the other produces the repro¬ 
ductive gland; the property in which the latter has the 
advantage, being the germ-plasm. 
Strasburger disputes this on the ground that the loops of 
the nuclear spindle after division, are exactly equal and 
similar in every way, and considers this an unanswerable 
fact on which he bases his own hypothesis ; yet Weismann 
argues with very good reason that, notwithstanding their 
undoubted equality as shown to the eye under the microscope, 
yet the resulting cell-bodies may be different in size, shape, 
and subsequent history, so that one must possess something 
that the other does not. 
His contention is supported by his recent observations on 
the Diptera, where the ovum is seen at the very commence¬ 
ment of segmentation to set apart a cell which subsequently 
becomes the reproductive gland. In this case we have the 
“ continuity of the germ-plasm” in a nut-shell, or rather egg¬ 
shell. 
As the theory does not admit of the possibility of the 
transmission of acquired characters, it is contended that the 
Natural Selection of spontaneous variations is sufficient for 
all change ; that variations arise only by means of the mixture 
of the inherited characters of the male and female. Each 
ovum and spermatozoon contains within it the accumulated 
traits of a long line of ancestors, which by developing together 
are sufficient to produce variations without limit. The progeny 
of one pair of dissimilar individuals would in the tenth 
generation exhibit their traits in 1,024 different combina¬ 
tions, and as every creature has more than ten ancestors the 
scope for variation is practically infinite. 
Then arises the question, “ How did the first differences 
occur?” They are supposed to have made their appearance 
amongst the unicellular organisms, for as they are practically 
immortal they are always under the influence of the environ¬ 
ment which impresses itself upon them, and any alteration it 
effects in them will be retained when they divide. Such a 
