688 JULIAN 8. HUXLEY 
The germ-cells are thus, in normal circumstances, partially 
dominant over the interstitial cells, and are also more susceptible 
than they are. This is the same relation that we found to hold 
good between the zooid and stolon of Perophora. Furthermore, 
it appears that in the testis a similar relation is to be found 
between the interstitial cells in their turn and the connective 
tissue (and Sertoli cells). Transplanted testes, as we have 
said, first lose their germ-cells and show increase of inter- 
stitial tissue. Within a few months the Sertoli cells also 
degenerate and disappear (Stemach, Sand). We may take 
this to mean that these cells, while not increasing after the 
loss of the germ-cells because they are not a multiplicative 
type of cell, are slightly less resistant than the interstitial 
cells. Even these, however, are less resistant to unfavourable 
conditions than the connective tissue. After a longer or 
shorter period (usually several months) in the abnormal 
situation, the interstitial cells in their turn start to decrease in 
number, and now it is the connective-tissue cells which show 
a corresponding increase. Finally, the ‘ testis’ comes to consist 
of nothing but connective tissue and blood-vessels. This is 
also seen in some few cases of cryptorchism. 
We have thus a system in which there enter four variable 
sub-systems. One of these, for a reason which we can conjecture 
but not prove, does not increase when others decrease. The 
other three, however, are all in that state of dynamic equilibrium 
which we have seen in its simplest manifestation in Perophora. 
But this time they are arranged in a series, A being physio- 
logically dominant over B, and B in its turn over C. Normally, 
therefore, the relative proportions of the three tissues are 
regulated according to the activity of A. When A is adversely 
affected B increases, but not C. C, however, increases when 
both A and B have been affected. 
If such a type of system were to exist, it should follow that 
in some (abnormal) circumstances somewhat different condi- 
tions should obtam, and that a slightly different end-result 
should be brought about. As a matter of fact, in some of the 
transplantations of Sand, this did occur. In three cases both 
