1397] FUNDAMENTAL PRINCIPLES OF HEREDITY 315 
come within the purview of the present article. As it is, the 
theory falls under the ever-trenchant blade of Occam’s razor, 
“ Entia non sunt multiplicanda praeter necessitatem.” 
The antagonistic school, of Herbert Spencer, regard Living Beings 
as characterised by their continuous adjustment of internal relations 
to external conditions, and cannot see 4 priori grounds for regarding 
the reproductive cells as especially lacking in this power of 
adaptation. They regard instinct as only explicable as_ habit 
transmitted and relatively fixed by constant transmission from one 
generation to the next, and are disinclined to admit (even as a formal 
hypothesis) any scheme that leaves all such considerations on one 
side. They therefore are compelled to refer variations in the offspring 
to the adaptive reaction of the parent to the environment, and hold 
that there must be some mechanism of transmission other than 
that of direct cellular inheritance, by which the reproductive 
cells hand down to their differentiated cell-offspring the characters 
of the corresponding cells in the parent organism as a whole. 
Charles Darwin felt this need so keenly (in a way largely ignored 
by those who style themselves his only true disciples) that he for- 
mulated his elaborate provisional hypothesis of Pangenesis to supply 
the mechanism that he postulated. He supposed that every cell in 
the body gave forth minute buds or ‘gemmules’ which circulated in 
the blood, and were carried by its current to the reproductive cells 
where they were stored up, and that in the development of the embryo 
they induced the formation of cells like those from which they were 
given off. Galton tried the crucial experiment of transfusing blood 
from one breed of rabbits to another, and found that this had no 
effect on the purity of the offspring. This not only shattered the 
theory of Pangenesis, but settled in the negative every conceivable 
theory of hereditary transmission based on the conveyance of formed 
material particles or of chemical substances from the other parts 
of the colonial organism to the reproductive cells.! 
The second theory is that of Herbert Spencer, of ‘biological units,’ 
of definite form and relation, which by their polarity tend to complete 
the organism. I shall describe that development of it recently put 
forward with great skill and ingenuity by Wilhelm Haacke under 
the title of the “Gemmaria theory.”? He holds that all living 
plasma is composed of minute units, the ‘gemmae,’ grouped 
together in aggregates, the ‘gemmaria, both being of definite form 
and size, in virtue of which they tend to assume certain relations of 
1“*Vife and Habit,” Lond. 1878; and ‘‘Unconscious Memory” (Lond., 1890). 
The latter work contains a translation of Hering’s paper. ‘‘ A Theory of Development 
and Heredity,” by Henry B. Orr (London and New York, 1893), is written essentially 
from this point of view. 
2 See ‘‘ Gestaltung und Vererbung,” Leipzig, 1893, and ‘‘Schépfung der Tierwelt.” 
Both these works are written in a German style of exceptional charm, ease, and 
vivacity. 
