282 THE HISTORY 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.) 
Srxtu Stace: Gliding Worms (Turbellaria). 
The human ancestors of the sixth stage which originated 
out of the Gastrzeada 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 
accelomatous worms did not as yet possess a true body- 
cavity (ccelom) nor blood. They originated in the early 
primordial period out of the Gastrzeada, 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 accelomatous 
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 primeval accelomatous 
Primary Worms. 
