8o The American Geologist. i'<-i)niar.v. ]'.»(>i. 
technical precision, with circumscribed questions. They in- 
volve great special knowledge and are based upon a careful 
comparison of observations along a particular line of zoolog- 
ical inquest. But the search for some general tendency, some 
broad teleological movement of forms, prevailing as a tec- 
tonic impulse over or through a diversity of animal groups 
has not been so extendedly followed. Such a search deals 
only with primary relations, as size, form, ornamentation, com- 
plexity, fecundity. 
It deals with more general and simpler questions and it 
seems reasonable to expect can be answered by an inspection 
simply of the work of the specialists. For, as Dr. Beecher has 
said (Origin and Significance of Spines) "the history of a 
group of animals is the same. The first species are small and 
unornamented. They increase in size, complexity, and diver- 
sity, until the culmination, when most of the spinose forms be- 
gin to appear. During, the decline, extravagant types are apt 
to develop, and if the end is not then reached, the group is 
continued in the small and unspecialized species, which did not 
partake of the general tendency to spinous growth." An ad- 
equate comparison then of the phylogenetic work done in dif- 
ferent sections of animal life might reveal general tendencies 
or laws. It is not difficult to see that it does. In this paper 
the suggestions are derived from an inspection of the Hall 
Collection. 
SIZE AND SKELETON MASS. 
It is evident that in any animal series the primary mem- 
bers are small. It is inconceivable that a group of animals 
where the members attain any considerable size can on its first 
appearance in geological time assume complete physical devel- 
opment. An inspection of the Lower Cambrian faunas shows 
this diminutiveness. With the exception of trilobites the 
forms are small. The genera I [^hidea, Acrotreta, Liunarssonia, 
LingiiJella, Kutorgina, OboJella, Orfhisina, Fordilla, the patel- 
loids, (Scenella, Stenotheca), and the pteropods(?) all ex- 
press molar immaturity. Organization preceded skeletal 
deposition. 
This fact has considerable interest and appears to contain 
suggestions of phylogenetic importance. If we find in a fossil 
