LAW OF ACCELERATION. 4] 
compressed, involute forms like Sehlot. Charmassci, the suppression, so far as we 
know, always occurred in normal forms at some nealogic stage, and the presence 
of a channel is constant even in the young. If the pile again crossed the 
abdomen, thus obliterating or obscuring the channel, during the life of the 
same individual, it occurred as a degradational character in the senile stages. 
Extreme cases of degradation in species did not occur in Schlotheimia, but if 
there had been any such nostologic forms, they would have inherited this ten- 
dency to obliterate the channel during the nealogic stages. The law of ac- 
celeration of development was quite as effective in its action upon geratologous 
as upon progressive characters, as will be seen when we treat of this class of 
characters farther on. 
Besides the examples given above of the inheritance of characters in larger 
and smaller series, we add the following in order to make our meaning still clearer. 
The form, shape, and characteristics of the secondary radical, Psi. planorbe, are 
prominently shown in the young of Arnioceras, Plate II. Fig. 10-15, and in the 
Embryology of Cephalopods, Plate II. Fig. 9, 10, until a late period of the 
growth of the shell, but are less noticeable in the young of the descendent 
species, Cor. kridion, in which indeed they are perceptible only in the transition 
form between this species and senzicostatum. Most of the specimens have young 
like that figured on Plate III. Fig. 2, and are stouter than the flat discoidal Psil. 
planorbe. These and the young of other species of Coroniceras inherit the stouter 
quadragonal whorl and peculiar ribs and tubercles, the keel, and the channels, 
at earlier stages of their growth than those in which they first appeared in ances- 
tral shells, as may be seen by comparing Arn. semicostatum with the young of 
Coroniceras, Plate III. Fig. 19, and Fig. 5, 6, 8-10. 
One of the most convincing examples of the law of acceleration which we 
have studied can be illustrated by using Wright’s book, “Lias Ammonites.”? He 
shows the latscostan form of the young on Plate XXXIV., and in Fig. 4-6 the 
adult of Androgynoceras hybridum, his Agoceras heterogencum. A more accelerated 
form is shown on Plate XXXV. Fig. 4-6, in which the young are similar to 
lateecosta for a less prolonged period of their growth. Wright's oc. Henleyi, 
Plate XXXIII., is also a specimen of the same species with a prolonged late- 
costan stage of growth. Lip. Henleyi, figured by Wright as Mgoc. striatum, 
Plate XLIIL, is also highly accelerated, and most of the specimens have young 
shells with no traces of their lateecostan ancestry, reproducing only the char- 
acteristics of the adult whorls of And. hybridum. Lip. Bechei, also figured by 
Wright, Plate XLIL, is still more accelerated in its mode of development, since 
the young has no resemblance to the adult of And. hybridum. From the smooth 
stage of the nxpionic period of growth it passes abruptly to a stage in which the 
shell resembles the adult form of And. Henley’. The whorls at this stage show 
the specific characters of the adult of And..Henleyi ; they are too involute and 
too heavily ribbed and tuberculated in proportion to their size to be compared 
with the adult of And. hybridum. 
Wiirtenberger’s book is devoted to the exposition of this law of heredity 
1 Paleontological Soc., XXXII., 1878. 
6 
