14 The Gemmutle vs. the Plastidule as the [January, 
Von Baer, Darwin, Spencer and Haeckel have given to the science 
new impulses and aims far higher than possessed its masters in 
its infancy. 
Dr. Darwin, in order to account for the phenomena briefly set 
forth in the above remarks, had recourse to what he called the 
“ Provisional Hypothesis of Pangenesis.’ The following is Mr. 
Galton’s brief statement of the hypothesis: 
. Each of the myriad — in every living body is, to a great 
cue an independent organi 
2. Before the cell is developed, and in all stages of its develop- 
ment, it throws “ gemmules ” into the circulation, which live there 
and breed, each truly to its kind, by the process of self-division, 
and that consequently they swarm in the blood in large numbers 
of each variety, and circulate freely in-it 
3. The sexual elements consist of organized groups of these 
gemmules. 
4. The development of certain of the gemmules in the off- 
spring depends upon their consecutive union through their natural 
affinities, each attaching itself to its predecessor in a natural order 
of growt 
5. That gemmules of innumerable varieties may be transmitted 
for an enormous number of generations without being developed 
into cells, but always ready to become developed, as shown by the 
almost insuperable tendency to feral reversion in domestic 
animals. 
Galton, in order to test the truth of the foregoing hypothesis, 
transferred the blood of different breeds of rabbits from one to 
_the other, actually establishing a cross-circulation, in which cases 
the blood flowing from one individual to another was practically 
unchanged. After this operation upon the animals, the young 
ones reared by these were not found to have been influenced in 
the slightest degree by the admixture of foreign blood with that 
already contained in the vessels of their parents, which should 
not have been the result were the hypothesis of pangenesis a true 
one. FPangenesis having been subjected to a crucial test and found 
= wanting, nothing was offered, as an avowed substitute, until 
the Plastidule, except by Prof. Cope, who, in his “ Origin of 
Genera” (Proc. Acad. Nat. Sci., Phila., 1868), and afterwards in a 
paper entitled “ On the Methods of Creation of Organic Types” 
_ (Proc. Am. Philos. Soc., 1871) more fully developed the views 
el Haeckel’s have been discussed. 
presented in the first mentioned. His views will be considered - 
_ Haeckel proposed his Provisional hypothesis of the Peregenesis of . 
