374 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
if tiles were placed there they would be instantly engulfed. These localities have, 
however, been reclaimed by a more or less recent process which forms a surface crust, 
macadam like, to give a suitable support for the collectors and their manipulators. 
This process, as at Kergurionne, though costly, has proven of practical value, as can 
be inferred from the extensive continuance of the practice. The very general use of 
the champignon collectors in the Auray (Morbihan) region is alone significant of the 
muddy character of the water, which renders of the utmost importauce the question 
of determining the exact time to put the collectors in place. In fact in all of the 
French regions of production silt deposit goes on so rapidly that the tile when in 
position is said to retain its value but little longer than a week; it is to be noted that 
even during this short time its upper surface has become unproductive and that 
the undermost tiles in many of the forms of collectors are very slightly, if at all, 
spat-bearing. 
Mobius maintains that the size of the banks in a given region can not be mate- 
rially augmented — a matter which is of great interest even from the standpoint of 
pure biology. Hot that it is at all to be questioned that a natural bank would under 
normal conditions remain more or less uniform in size and in the proportion of its 
component organisms — but it is the theory involved in this question that seems 
to the writer susceptible of broader interpretation than has been assigned it. 
Bioccenosis is the term applied by Mobius to express the mutual interdependence of 
species existing in a colony— a condition of happy- family existence in a natural cage 
whose limited food supply locks up the chances of permanent numerical increase. In 
accordance with this keenly poised life-balance Mobius infers that the banks of the 
Wattenmeer can not be permanently added to, even by artificial means (Auster u. 
Austernwirthschaft, p. 78). He notes, for example, that a season favorable to oysters, 
will, per se. cause the oysters during the following seasons to fall back to their normal, 
inasmuch as food material has thus been prepared for the enemies (crab and starfish) 
whose increased progeny will restore the balance of life. 
The important inferences drawn from this doctrine of life-balance, do not, how- 
ever, seem to be entirely warranted by the premises. We are led, for example, to 
infer that individuals are dependent upon the colony, and that the colony holds the 
curb, checking the permanent increase of one form at the expense of another. On the 
other hand, struggle for survival is undoubtedly the democracy of animal living, and 
in these days it has been pretty clearly established that the colony is but an incident 
more or less transient in the survival of the fittest. So the biocoeuose, as we must 
accordingly admit, becomes but an episode in colonial life, whose duration depends 
upon the enduring force of its component species, where quickly moving predatory 
forms have the right of might, where stationary and defenseless forms have become 
mimics to escape their enemies, or have developed a surprising fecundity to survive 
the dangers of a compressed living-area or unfavorable environment. It can not at 
present be doubted that the scale of the struggle may readily be turned in favor of 
but a single type or species. Artificial devices may thus become the rapid undoing 
of the slowly struggling biocoenose, for they favor the protected species and would 
not unreasonably tend to blot out the accompanying enemies of this form. 
