( c ) 
undertaken by Tower, there are some which have a direct 
bearing on the matter under consideration. Of these I propose 
to give a brief account. It should be premised that the 
beetles of the genus Leptinotarsa lay their eggs in batches, 
each batch being laid before the next begins development. 
Experiment 1.—Males and females of L. decemlhieata were 
exposed to extremely hot and dry conditions, accompanied by 
low atmospheric pressure, during the growth and fertilisation 
of the first three batches of ova. These were reared from the 
outset in normal conditions. Out of 96 specimens so obtained, 
82 were of the varietal form pallida. After the deposition of 
the first three batches of ova, the same parent beetles were 
placed in normal conditions, and two more batches were laid. 
These, reared under natural conditions, gave normal decem- 
lineata, which continued to breed true to type. The origin of 
the pallida forms may therefore fairly be ascribed to the 
abnormal conditions to which their parents were for a time 
exposed. Two of these pallida males were mated with decem- 
lineata females; the resulting hybi’ids resembled normal 
decemlineata. Kow comes an interesting point. This genera¬ 
tion of apparently normal decemlineata gave, when bred inter 
se, offspring consisting of pallida, decemlineata, and decem- 
lineataA\kQ hybrids in Mendelian proportion. The pallida of 
this generation bred true, being evidently extracted recessives; 
the decemlineata and hybrids broke up again in Mendelian 
fashion. This most interesting experiment points to at least 
three results of great biological importance. The first, which 
is that in which we are more immediately interested, is the 
confirmation of Weismann’s view as to the accessibility of the 
germ-plasm to external influences. The second is the demon¬ 
stration that just as the somatic plasm has a period of highest 
susceptibility, which fact was known to Weismann at the 
time of his G. jMaeas experiments, so also the germ-plasm 
itself has a similar period. This was not known to Weismann ; 
if it had been, it might have led him to modify in some 
respects his conclusions from those experiments. The third 
point is the establishment of the fact that the type-form 
of a given species may stand in Mendelian relation with a 
variation of that species artificially induced by interference 
