616 
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, 7. 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 Nautilinidz 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 
Goniatitinze of the Devonian and of all of the remaining Ammonoids 
to the end of the Cretaceous. 
g. 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. 
