88 The American Geologist. February, looi. 
carapaced, sessile, and seminatatory forms in deeper water. 
This assumption is hardly violent to those who have 
watched the tendency of recent biological speculation. Ernst 
Haeckel in his History of Creation pointed out the archetypal 
character of the metameral vermes ; "the phylum of Worms, 
on the other hand we have to conceive as a low bush or shrub, 
out of whose root a mass of independent branches shoot up in 
different directions. From this densely branched shrub, most 
of the branches of which are dead, there rise four high stems 
with many branches. These are the four lofty trees just men- 
tioned as representing the higher phyla — the echinodermes, Ar- 
ticulata, Mollusca, and Vertebrata. These four stems are di- 
rectly connected with one another at the root only, to-wit, by 
the common primary group of the Worm tube." In the com- 
munication of Prof. J. Beard of the Anatomisches Institut, 
Freiburg, to Nature (Vol. XXXXIX, p. 259) on "Some An- 
nelitlan Affinities in Ontogeny of the \^ertebrate Nervous 
System" he remarks that "if we are ever to trace the ancestry 
of \'ertebrates at all, the nervous system will probably form a 
significant factor in the solution." But it is the arthropods 
which resemble the ringed worms in possessing "a very cJiar- 
actcristic form of the central nervous system, the so-called ven- 
tral marrow, which commences in a gullet-ring encircling the 
mouth." (Haeckel). If the nervous system then is an index of 
affinity, it serves in the case of the crustaceans to point also to 
their annelidan origin. Gegenbaur (Comparative Anatomy) 
shows that. He says "the nervous system of the Arthropoda 
resembles that of the Annelides with which it completely agrees 
in its fundamental characters." Simroth says emphatically "so 
entirely can we see the agreement of the ancient animals in a 
sum of features that, without further effort to unite them, we 
demand a common root for their common derivation. What 
was this ? No one can conceive of anything else than an Anne- 
lid, and certainly, because of the development of the necessary 
paropodia for the growth of the articulate members, of a marine 
Polychaeta." 
The pre-Cambrian age was the age of Worms. The rocks 
of the Cambrian offer evidence of this. The annelidan traces 
in the Potsdam slates and sandstones, shales and flags exceed 
those of any similar beds throughout the palaeozoics. 
