928 The American Naturalist. : [November, 
much flattened, as flounders, for example, besides being usually 
mimetically colored. In these cases the figure of the body is 
so obviously correlated respectively with a capacity for a high 
velocity of motion and a capacity for only a low velocity of 
motion that there seems to be reason to suspect that the figure 
of the body is also correlated with a widely varying intensity 
of conflict with enemies and conditions in the struggle for _ 
existence, such as seems to be established by the various geo- 
metrical laws of their space relations during that conflict or 
struggle. If there have been forms which have developed in — 
such directions as to give them greater celerity and conse- 
quently greater command over their surroundings in every 
direction there have been others which have been equally suc- 
cessful, often by the aid of mimicry, in getting into out-of-the- 
way corners and hiding-places in Nature where the possible 
number of approaches from their enemies have been also 
greatly reduced. Which of the two is the most advantageously 
situated it would be difficult to decide. For, while the swift 
and alert type must expend a great amount of energy in 
motion, the sluggish and concealed must vegetate and in a 
sense continually tend to degenerate in some one or other 
respect. The comparative rarity with which free-swimming 
or pelagic forms develop a tendency to bud or throw out 
stolons is perhaps to be connected with the great amount of 
energy expended in setting up motion. Where such colonial 
forms are mobile, most, be it observed, are obviously adapted 
as colonies for such motion, as the Siphonophora, chain Salpæ 
and Pyrosoma, for example. In other cases: sessile Protozoa 
Porifera, Coelenterata, Tunicata, loss of active, free motility 
seems to end in a tendency to produce buds and stolons and 
develop colonial forms. It would seem as if the material and 
energy expended by the freely moving forms in active motion 
prevented the development of stolons and coherent colonies, 
intensified their specialization for active motion, and in some 
cases reduced their fertility. In the case of sessile forms or 
those with quiescent habits it would seem that the consequent 
saving of the material and energy of motion was compensated 
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