PRESIDENT’S ADDRESS. 349 
floats near the surface of the sea. This pelagic aspect of the early 
faunas is carried out by the Mollusca of the Algonkian and Cam- 
brian periods as well as by the great development of free-swimming 
Medusz in the Cambrian ; and we should remember that these 
delicate pelagic animals must have been very numerous to have 
left any record at all. 
The earliest known Radiolarians are accompanied by the remains 
of sponges which must have lived on the bottom of the ocean, and 
these were followed by creeping worms and Trilobites. The early 
Brachiopods have diaphanous shells, like the pelagic mollusca, 
but it seems probable, from a study of their development in living 
forms, that at first they had no shell at all, but consisted of the 
peduncle encased in a sand-tube. The shell was afterwards added 
to protect the branchiz, and in course of time the intestinal tract 
in the peduncle atrophied. Perhaps the so-called annelid tubes of 
the Torridon sandstone represent the first Brachiopods. 
From all this we may infer that the first animals were pelagic 
protozoa which, in time, varied and gave rise to pelagic worms 
and mollusca. At a very early date, however, some of the protozoa 
followed down the dead organisms and settled on the bottom, 
giving rise to the sponges. Afterwards worms moved in the same 
direction, feeding, probably, on the sponges ; and from them are 
descended the Brachiopods and the Crustaceans.* 
The remains of the Brachiopods and Trilobites are found 
chiefly in shallow-water deposits, but some of them may have 
pushed their way into the deep sea, feeding on the dead pelagic 
organisms which rained down from above ; indeed, it has been 
thought that the eyeless condition of some of the early Trilobites 
is a proof of this. But the eyes are always placed on the second 
segment, called the free cheek, and in several of the earlier forms 
this free cheek is ventral only, in which case no eyes could appear 
on the dorsal surface ; the absence of eyes is not, therefore, always 
a proof of degeneration, but there are some species of Paradoxides 
in which it is said that the eyes have become rudimentary. 
The hard spines of the early Trilobites could not have been for 
defence, for there were no enemies capable of attacking them ; but, 
perhaps, they were used indirectly in locomotion. As their weak 
little legs paddled backwards and forwards in the mud the spines, 
all of which are directed backwards, would necessitate motion in 
a forward direction only. 
There is no evidence of the existence of any animals sufficiently 
protected to live among the breakers round the shore, nor is there 
any evidence of life on the land. Ifa human spectator could have 
stood on the shore at that time he would probably have seen no 
* This theory was originated, I think, by Biologists, and was first brought prominently 
before Geologists by Professor W. K. Brooks, in the American Journal of Geology for July 
and August, 1894. 
