THE EARLIEST ANIMALS. I25 



portant fact that the egg of all animals, from those of sponges 

 and worms up to those of the ant and man, is a simple ceU. 



Thirdly, from the " single-cell " state arose the shnplest 

 multicellular state, namely, a heap or a small community of 

 simple, equiformal, and equivalent ceUs. Even at the present 

 day, in the ontogenetic development of every animal egg- 

 cell, there first arises a globular heap of equiformal naked 

 cells, by the repeated self-division of the primary cell (Com- 

 pare vol. i. p. 190 and the Frontispiece, Fig. 3.) We called 

 this accumulation of ceUs the mulberry state (Morula), 

 because it resembles a mulberry or blackberry. This Morula- 

 body occurs in the same simple form in all the different 

 tribes of animals, and on account of this most important 

 circumstance we may infer — according to the biogenetic 

 principle — that the most ancient, many-celled, primary forin 

 of the animal kingdom resembled a Morula like this, and 

 was in fact a simple heap of Amoeba-like primaeval cells, 

 one similar to the other. We shall call this most ancient 

 community of Amoebae — this most simple accumulation of 

 animal ceUs — which is recapitulated in individual develop- 

 ment by the Morula — the Synamceha. 



Out of the Synamoebse, in the early Laurentian period, 

 there afterwards developed a fourth primary form of the 

 animal kingdom, which we shall call the ciliated germ 

 (Plansea). This arose out of the Synamoeba by the outer 

 cells on the surface of the cellular community begioning to 

 extend vibrating fringes called cilia, and becoming " ciliated 

 cells," and thus differentiating from the inner and unchanged 

 cells. The Synamcebse consisted of completely equi- 

 formed and naked ceUs, and crept about slowly, at the 

 bottom of the Laurentian primaeval ocean, by means 



