Adaptations in Tissue Structure 203 
ment of even a single species, and still less, if that is 
possible, concerning the true mode of procedure of this 
natural selection which is so difficult to control. So that 
we must content ourselves with putting forward the views 
which we have just outlined merely as further con- 
jectures speaking in favor of the Lamarckian theory, 
without seeking to attribute to them the value of logical 
proof. 
Structural relations in general and the most remark- 
able ones in particular, such as the static structure of 
bone, of certain tendons, of certain membranes, the 
dynamic structure of the smooth and striated muscle 
tissues and other similar formations, which represent the 
most perfect functional adaptation and the best utilization 
of the material down to the minutest and most delicate 
details, testify likewise in favor of the transmissibility 
of acquired characters. “All these formations of con- 
nective tissue, muscle and bone,” writes Roux, “could 
never have been developed in such regularity and com- 
pleteness by Darwinian selection from individual varia- 
tions of form, since here there must necessarily have 
been thousands of fibers and cellules already accidentally 
arranged in this purposeful fashion in order to produce 
even the smallest advantage appreciable in the economy 
and capable of being acted upon by natural selection, and 
so much the more since in the extremity of hunger these 
would be exactly the parts, the heart excepted, which, 
thanks to the small amount of metabolism in them, 
would suffer last of all,—much later than other more 
vitally important organs with more active metabolism. 
These formations could not therefore arise from the 
selection of individual variations in form, but are rather 
derived only from those qualities of the respective tissues 
