76 
Transactions Texas Academy of Science. — 1906. 
represents a mass of waste products that have resulted from the 
metabolism of the parent individual, a part that becomes intoxined 
by the accumulation of excretions. Sporulation is, accordingly, an 
action of escape of uncontaminated parts from a mass that is em- 
poisoned. Unless there were some such active escape of parts the 
whole would become poisoned, and the race meet its end. The 
initial stimulus to sporulation is then probably the effect of this 
residuum upon the remainder of the substance. "We may say that 
such generation is an act of excretion by the offspring, in this case 
the spores — they rid themselves of these waste materials by moving 
away from them. 
Sporulation is the kind of reproduction that is probably of most 
extensive occurrence in the Protozoa, and is especially characteristic 
of the multiform groups of the Sarcodina and Sporozoa. In it also 
the mode of nuclear division is frequently of a very simple kind of 
mitosis. For these reasons I have taken the stand that it is the 
most primitive kind of reproduction in the Protozoa, for budding 
is far less usual, may be entirely lacking in the life cycles of various 
groups, and is clearly a secondary mode of generation. And binary 
fission, though generally regarded as the primitive process, is far 
from being a simple act, for division into two approximately equal 
parts is an act of great precision, far more so than is sporulation, and 
so is the intricate preformation of s parts before separation of the 
daughter individuals. Just as with increasing bodily specialization 
reduction in the number of parts frequently denotes progress toward 
a complexer condition, so division into exactly two parts may be 
an advance beyond division into many parts. 
Fission results in the division of the parent into two parts, each 
of which continues to live; here there would then appear to occur 
generation not associated with death of any part. But the process 
of fission cannot repeat itself indefinitely for either it alternates with 
other kinds of reproduction that are associated with death, or else, 
as notably in the case of Paramoecium, it cannot continue without 
the application of a powerful stimulus associated with change of 
substance, such as increase or modification of food or an act of con- 
jugation with another individual. Though no residuum is left be- 
hind in fission, yet there may be disintegration and probably death 
of some of the substance, as shown by the fragmentation and digestion 
of the macronuclei of the Ciliata. Even in fission therefore some 
part of the parent dies. Fission probably also subserves the ends 
of excretion by increasing the body surface. 
Budding is the act where smaller parts are cut off from a larger 
one ; in this case the parent individual can continue this process for 
