On Reproduction, Animal Life Cycles. 
79 
was right in concluding: “ Somatic cells are simply cells in which 
the activity of the hereditary impulse is inhibited in consequence of 
their senescence, or, in other words, differention ; ” but he failed to 
name the underlying factor of senescence, which is insufficiency of 
the excretion process. 
Prior, however, to the complete death of this specialized part, the 
residuum or soma, a part or parts escape from the empoisoned mass 
and constitute the beginning of a new generation. Therefore the 
essential connection of death and reproduction is the separation of 
living matter from a dying portion. Generation may itself, accord- 
ingly, be considered an act of excretion on the part of the germ, for 
the latter separates from a mass vitiated by waste products. Though 
the body may appear to mechanically discharge the germs, and in 
the higher organisms has secondarily come to do so, the process there- 
fore appears to pertain to the body, yet primitively the germs were 
the active movers in the act. The process is clearest in the Protozoan : 
in sporulation motile bodies automatically separate from an inert 
residuum, and are in no way discharged by the latter. In the Meta- 
zoa it is merely less simple in that the germs bring an indirect in- 
fluence to bear upon the soma, that causes, the soma to emit them. 
But in many Metazoa an automatic separation of germ cells from the 
body is still found to occur, as when by their accumulation in num- 
ber and increase in size, in an Annelid or a Nemertine e. g., they 
actively rupture the body wall; the same process holds for some cases 
of so-called viviparous birth. 
Without doubt reproduction can be interpreted in a variety of 
ways, as it has in the past. Nevertheless the phenomenon is remark- 
able that the germ cells, either by their own locomotion or by ex- 
truding substances that stimulate the soma to their removal, separate 
from an intoxined part. Germ cells do not leave the body until it 
is in a relatively advanced condition, until specialization of parts 
has commenced. This phenomenon is given its just due when we 
conclude that reproduction is an act of excretion on the part of the 
offspring. In many of the lower animals, for instance most insects, 
the somatic individual may die soon after the act of generation, even 
though this may have effected no bodily lesion. Generally this has 
been interpreted to mean that the individual dies because of the 
harmful influences upon it of the act of generation. Yet such an 
explanation is quite askew; the germ cells leave the individual be- 
cause the latter is on the road to death. For if a mature insect be 
prevented from procreating it will die notwithstanding. In some 
animals, on the other hand, the body does not die after one act of 
generation, but may live through a succession of them, extending 
