PARALLELISM OP ONTOGENY AND PHYLOGENY. 1 27 



Definition of ihe 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 contaiaing a 

 kernel.) 



Third Stage of Develop, 

 ment. 

 A commnnity (an 

 aggregation of identi- 

 cal simple cells) . 



Fourth Stage of Develop- 

 ment. 



A solid or bladder, 

 shaped, globular, or oval 

 body, composed of two 

 Icinds of different cells : 

 externally ciliated, in- 

 ternally non - ciliated 

 cells. 



Fifth Stage of Develop- 

 ment. 



A globular or oval 

 hody xoith 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 (gaatral layer) , 



Ontogenesis. 

 The five first stages 

 of the individual de- 

 velopment. 



Uonerula. 

 Animal egg without a 

 kernel (when the egg- 

 kernel has disappeared, 

 after being fructified). 



2. 

 Ovnlum. 



Animal egg with ker- 

 nel (a simple egg-cell). 



3. 



Morula. 



{Mulberry form.) 

 Globular heap of ho- 

 mogeneous " cleavage 

 spheres." 



I 



4. 

 Pianola. 



{Ciliated larva.) 

 Many - celled larva 

 without mouth, com- 

 posed of different cells. 



Gastrola. 



{Larva with mouth.) 

 Many-celled with in- 

 testines and mouth; in. 

 testinal wall with two 

 layers. 



Phylogenesis. 

 The five first stages 

 ot the phyletio or his- 

 torical development. 



1. 



Moneron. 



Most ancient animal 



Monera, originating by 



spontaneous generation. 



2. 

 Amoeba. 



Animal Amcebse. 



3. 

 Synamoeba. 

 An aggi-egation of 

 Amcebse. 



4. 

 Plansea. 



Many - cell ed prim- 

 animal without 

 mouth, composed of 

 two kinds of different 

 cells. 



Gastraea. 



Many - celled prim, 

 aeval animal with intes. 

 tine and mouth ; intes. 

 tinal wall with two 

 layers. (Primary form 

 of zoophytes and 

 worms.) 



