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 skull-less and brain- 
less ancestors of man, is furnished by the comparative 
anatomy and the ontogeny of the Amphioxus and of the 
Craniota. 
TENTH SrTaGE: 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 mo<t imper- 
fect nature. The lowest stage of all 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 skull. 
The certain proof that such single-nostriled and jawless 
ancestors of man did exist,is found in the “comparative 
anatomy of the Myxinoidea.” 
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