96 : PROTOZOA. 
The degenerate state of the conjugation appears to be of a similar 
nature to the degenerate sexual process in certain low fungi, such as 
Saprolegnia, in each probably an effect of parasitism. In each case 
there is a sort of imitation of the real process although the essential 
interchange of nuclear material is absent. 
The sporocyst finally bursts and the coated spores are 
set free out of the anus of the cockroach. Protected by 
the hard coat these spores lie dormant till any 
of them happen to be introduced with food 
into the intestine of another cockroach. In this event the 
spore-case bursts and its contents escape as a creeping 
amceboid nucleated mass of protoplasm. This works its 
way into the epithelial cells of the cockroach’s intestine 
and there remains for some time. It is then termed an 
intracellular parasite, living wwéthixn the epithelial cell. 
Here it grows and assumes the elongated form and other 
characters of the adult. Contemporaneously it gradually 
protrudes from the cell into the lumen of the intestine, 
still attached by the anterior end with its cap. Finally it 
becomes detached and lives free in the lumen or cavity of 
the intestine. 
Life history. 
We may note that there is a definite limit to the number 
of gregarines which can dwell in one cockroach, and when 
this limit is reached the gregarines would perish with their 
host. Hence the gregarines and all endoparasites must 
at some time, if the species is to be maintained, migrate 
and by some means reach a fresh host. This is not 
essentially different from a sheep moving to fresh pasture 
after having exhausted the previous one, but in the former 
case the probabilities of reaching the fresh scene of action 
are infinitely less. The difficulties of the migration are 
overcome in two ways :—Firstly, an enormous number of 
the migrating units are produced just before the migration, 
the number roughly corresponding to the probabilities of 
survival; secondly, the migrating units are protected for 
their hazardous journey by hard coats or cases. In these 
respects the gregarine is typical of endoparasites. (See also 
Parasitism, Chapter IX.) 
