286 THE HISTORY OF CREATION. 



neutral stages) exhibited the condition of hermaphrodites 

 (hermaphroditism). (Compare vol. i. p. 196.) The certain 

 proof of the former existence of these skuU-less and brain- 

 less ancestors of man, is furnished by the comparative 

 anatomy and the ontogeny of the Amphioxus and of the 

 Craniota. 



Tenth Stage : Single-nostriled Animals (Monorrhina). 



Out of the Skull-less ancestors of man there arose in the 

 first place animals with skulls, or Craniota, of the most imper- 

 fect nature. The lowest stage of aU still living Craniota is 

 occupied by the class of round-mouthed animals, or Cyclos- 

 toma, namely, the Hag (Myxinoidea) and Lampreys (Petro- 

 myzontia). From the internal organization of these single- 

 nostriled animals, or Monorrhina, we can form an approxi- 

 mate idea of the nature of the human ancestors of the tenth 

 stage. In the former, as also in the latter, skull and brain 

 must have been of the simplest form, and many important 

 organs, as for example, the swimming bladder, the sympa- 

 thetic nerve, the spleen, the jaw skeleton, and both pairs of 

 legs, may probably as yet not have existed. However, the 

 pouch gills and the round sucking mouth of the Cyclostoma 

 must probably be looked upon as purely adaptive charac- 

 teristics, which did not exist in the corresponding stage of 

 ancestors. The single-nostriled animals originated during 

 the primordial period out of the skull-less animals by the 

 anterior end of the dorsal marrow developing into the brain, 

 and the anterior end of the dorsal chord into the sktdl. 

 The certain proof that such single-nostriled and jawless 

 ancestors of man did exist, is found in the " comparative 

 anatomy of the Myxinoidea." 



