Paleoulologica! Speculations. — Grafacap. 2iy 
Fish were absent in the Cambrian seas, mohusca had 
reached no formidable growth, the shores were devoid of ex- 
cessive algous occupancy, and probably thermal conditions 
were benign. 
If we assume for the trilobite the fecundity of the ordi- 
nary crustacean, which in the lobster presents a phenomenal 
intensity since to the enormous number of ova in a female, 
the practical impregnation of every egg superinduces an al- 
most unparalleled generative success, and if we add to this 
the most optimistic circumstances of its environment, the 
great development, wide distribution, and individual num- 
bers of the Cambrian trilobites does not seem so extraordi- 
nary. In other words a biological crisis is coincident with 
the period of greatest internal and external harmony. When 
with the congenital forces of procreation, the physical fac- 
tors are so encouraging and sympathetic as to give them their 
extreme amplitude of action, the zoological result must at 
least be surprising. 
In Semper's contributions to the influence of surround- 
ings upon the animal organism (International Science Ser- 
ies, 1881) he has pointed out the varying influences of food, 
temperature, atmosphere, water motion, currents, subsidence 
and upheaval, ocean waves, pressure, and the influence of 
living surroundings. Amongst these for the purpose of real- 
izing the possible biological results amongst the trilobites of 
the Cambrian we may select food, temperature, water motion, 
currents, land movements and living surroundings. These 
must all have been reasonably favorable, and we can from 
geological evidence establish their probable coexistence and 
reinforcement. 
The crustaceans of the sea today feed upon algae and 
young marine animals. The Cambrian sea doubtless furn- 
ished algae in abundance oi a unicellular type but more es- 
pecially there is reason to think that protozoon, metazoon, 
and coelenterate life was omnipresent, and if the contention 
raised in the former section of this paper that the sea shores 
witnessed the earliest evolution of marine life, here rhizo- 
pods, sponges, medusse, jelly-fish, anemones, today vora- 
ciously eaten by lobsters and crabs would have abounded 
