282 THE HISTOEY OF CREATION. 



man. A certain proof of this is furnished by the Amphioxus, 

 which in spite of its blood relationship to Man still passes 

 through the stage of the gastrula with a simple intestine 

 and a double intestinal wall. (Compare Plate X. Fig. B 4.) 



Sixth Stage : Gliding Worms (Turbellaria). 



The human ancestors of the sixth stage which originated 

 out of the Gastrseada of the fifth stage, were low worms, 

 which, of all the forms of worms known to us, were most 

 closely allied to the Gliding Worms, or Turbellaria, or at least 

 upon the whole possessed their form value. Like the Tur- 

 bellaria of the present day, the whole surface of their body 

 was covered with cilia, and they possessed a simple body 

 of an oval shape, entirely without appendages. These 

 acoelomatous worms did not as yet possess a true body- 

 cavity (coelom) nor blood. They originated in the early 

 primordial period out of the Gastrseada, by the formation 

 of a middle germ-layer, or muscular layer, and also by the 

 further differentiation of the internal parts into various 

 organs ; more especially the first formation of a nervous 

 system, the simplest organs of sense, the simplest organs 

 for secretion (kidneys) and generation (sexual organs). The 

 proof that human ancestors existed of a similar formation, 

 is to be looked for in the circumstance that comparative 

 anatomy and ontogeny point to the lower acoelomatous 

 Worms as the common primary form, not merely of all 

 higher Worms, but also of the four higher tribes of 

 animals. Now, of all the animals known to us, the 

 Turbellaria, which possess neither a body-cavity nor blood, 

 are most closely allied to these primaeval acoelomatous 

 Primary Worms. 



