PARALLELISM OF ONTOGENY AND PHYLOGENY, 
Definition of the forms 
of the five first stages 
of the development of 
the animal body, 
First Stage of Develop- 
ment. 
A simple cytod (a 
plastid without a ker- 
nel.) 
Second Stage of Develop- 
ment. 
A simple cell (a 
plastid containing a 
kernel.) 
Third Stage of Develop- 
ment. 
A community (an 
aggregation of identi- 
cal simple cells). 
Fourth Stage of Develop- 
ment. 
A solid or bladder- 
shaped, globular, or oval 
body, composed of two 
kinds of different cells: 
externally ciliated, in- 
ternally non - ciliated 
cells. 
Fifth Stage of Develop- 
ment, 
A globular or oval 
body with simple intes. 
tinal cavity and mouth. 
opening. Body wall com- 
posed of two layers; an 
externally ciliated ecto- 
derm (dermal layer), an 
internally non - ciliated 
entoderm (gastrallayer), 
Ontogenesis. 
The five first stages 
of the individual de- 
velopment. 
i 
Monerula. 
Animal egg without a 
kernel (when the ege- 
kernel has disappeared, 
after being fructified). 
a 
Ovulum. 
Animal egg with ker- 
nel (a simple egg-cell). 
3. 
Morula. 
(Mulberry form.) 
Globular heap of ho- 
mogeneous “ cleavage 
spheres.” 
4. 
Planula. 
(Ciliated larva.) 
Many - celled larva 
without mouth, com- 
posed of different cells. 
5. 
Gastrula. 
(Larva with mouth.) 
Many-celled with in- 
testines and mouth; in- 
testinal wall with two 
layers. 
127 
Phylogenesis. 
The five first stages 
ot the phyletic or his- 
torical development. 
be 
Moneron. 
Most ancient animal 
Monera, originating by 
spontaneous generation. 
2. 
Ameba. 
Animal Amcebs. 
3. 
Synameba. 
An aggregation of 
Ameebee. 
A, 
Planea. 
Many-celled prim. 
eval animal without 
mouth, composed of 
two kinds of different 
cells. 
5. 
Gastrea. 
Many-celled prim. 
zeval animal with intes. 
tine and mouth ; intes. 
tinal wall with two 
layers. (Primary form 
of zoophytes and 
worms.) 
