Personal and ScientiGc News. 195 
the plateau and not far from the garnet zone the second 
along the foot of the ])lateau and best shown on the prop- 
erty of Judge Tucker. 
The paper of Dr. C. P. Berkey is printed in the Journal 
of Geology, Jan. -Feb., 1905, vol. 13. 
The last paper of the evening was by professor A. W. 
Bragau, on the "Evolution of Some Devonic Spirifers." 
Spirifer mucronatus (Conrad) is a Linnaean species com- 
prising a large number of mutations. A remarkable fact is 
that all mutations pass through a mucronate stage such as 
is characteristic of the adult mutation after which the 
species is named. (The term mutation is here used in the 
sense in which it was originally proposed by Waagen, and 
not in that in which it was subsequently used by De Vries ; 
i. e., for the result and not for the process.) A still earlier 
stage in development (nepionic) shows the non-mucronate 
features of the ancestral species similar to S. duodenarius 
of the Onondaga. The mucronate feature is carried to 
excess in a number of mutations of the Lower Hamilton 
group. It is especially persistent in the Michigan region. 
This type jf outline is actompanied by a rib in the median 
sinus and a depression in the fold. In Ontario the primi- 
tive mucronate type gives rise upward to a number of mu- 
tations which are especially characterized by progressive 
increase in bight without corresponding lengthening of the 
hinge. The median plication and depression quickly dis- 
appear. 
Acceleration and retardation in development are the 
chief principles which explain the development of the great 
number of mutations. For the principle of retardation the 
term bradygencsis was proposed, corresponding to the 
term iachygenesis proposed by Hyatt for acceleration. 
In the Xew York province the primitive mucronate 
type gives rise to high and short-hinged mutations, but 
these retain the median rib and depression. In form these 
are tachygenetic ; in respect to the surface features, brady- 
genetic. In the arenaceous beds of the later Hamilton 
in eastern Xew York, a mutation with many ribs and moder- 
ate mucronations exists. This is in many respects a brady- 
gentic type. Side by side with extremely accelerated or 
tachvgenetic types in all horizons (i. e., very short-hinged, 
non-mucronate, high and thick mutations) occur slightly 
retarded or bradygenetic types which retain in the adult 
the mucronate character which is typical of the young of 
all the mutations. 
The Field Columbian Museum will have the following 
course of lectures : March 4, "The Explanation of Indian 
Ceremonies," Dr. G. A. Dorsey; March 11, "Giant Reptiles 
