880 Values of the Stages of Growth and Decline. 
without danger of confusing them with the characters of any of the 
silphologic stages. 
After the silphologic and nealogic stages have been disposed of 
there still remains the adult period, which is equally important in 
genealogical investigations, since it enables the observer to study 
the origin of many characters, which afterwards become silphologic 
and nealogic in descendent forms. 
It is not uncommonly assumed, that adaptive characters appear- 
ing in embryos and larve are apt to be transient and have but 
little effect on the subsequent history of the early stage in the same 
group; also, that such characters have appeared just as readily in 
the larvee as in adults. Up to the present time this has not been - 
found to be true among fossil Cephalopoda, and there exist, so far 
as known to the author, but few characteristics probably originating 
in the early stages. The constant recurrence of hereditary charac- 
teristics in silphologic and nealogic stages which originated in 
adults, like those given above for the Endoceratide, makes the 
probability of the assumption, that the asiphonula and veliger 
represent the adult stages of lost types, so highly probable, that the 
burden of proof must rest upon the opponents of this argument. 
Each case of the origin of characters in embryo and larve should in 
other words be regarded with distrust until proven. 
The appearance of the incomplete modes of segmentation in 
existing Sepioidea may possibly be a case of origination in embryo. 
There are no adult forms known to the author, which store up food 
in their tissues in such a manner that they can be used to explain 
the origin of the specialized food yolk. Nevertheless special inquiry 
might have very unexpected results. The case above given of the 
calcareous nature of the protoconch, and all the other characters of 
the stage in the Ammonoids and Belemnoids, seemed to have 
originated in embryo until it was found that a distinct  silphologi¢ 
stage, the asiphonula, existed in Nautiloids, and that this indicated 
the former existence of an asiphonulate ancestor having a calcareous 
shell. 
Some of the characters of the goniatitinula, such as the deep 
ventral saddle of the first septum in the angustisellate young, te 
described by Branco, doubtless originated in the younger stages. 
These are, however, correlative with the anarcestian form of this 
