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when it is considered as a transmitted, tachygenetic characteristic 

 derived from ancestral, nautilian shells of the Jura, which have the 

 same characteristic at a later age, i. e., in the paranepionic substage. 



7. The first conclusion is also sustained by the parallel phylogeny 

 of the impressed zone in the ancestral forms of the Ammonoidea, 

 the Nautilinidae and especially in Mimoceras, the radical genus of 

 this family. 



8. The fourth, fifth and sixth conclusions are also supported by the 

 presence of a contact furrow on the dorsum of the earliest age of 

 the conch in the specialized and highly tachygenic forms of the 

 Goniatitinae of the Devonian and of all of the remaining Ammonoids 

 to the end of the Cretaceous. 



9. These cumulative results favor the theory of tachygenesis and 

 diplogenesis, and are opposed to the Weissmannian hypothesis of 

 the subdivision of the body into two essentially distinct kinds of 

 plasm, the germplasm, which receives and transmits acquired char- 

 acteristics, and the somataplasm, which, while it is capable of ac- 

 quiring modifications, either does not or cannot transmit them to 

 descendants. 



