e to explain the
action of habits and use of parts. "Je ne rappellerai par l'histoire
tant de fois critique du cou de la giraffe et des cornes de l'escargot."

Another important factor in the evolution of the metazoa or many-celled
animals, from the sponges and polyps upward from the one-celled forms or
protozoa, is the principle of animal aggregation or colonization
advanced by Professor Perrier. As civilization and progressive
intelligence in mankind arose from the aggregation of men into tribes or
peoples which lived a sedentary life, so the agricultural, building, and
other arts forthwith sprang up; and as the social insects owe their
higher degree of intelligence to their colonial mode of life, so as soon
as unicellular organisms began to become fixed, and form aggregates, the
sponge and polyp types of organization resulted, this leading to the
gastraea, or ancestral form from which all the higher phyla may have
originated.

M. Perrier appears to fully accept Lamarck's views, including his
speculations as to wants, and use and disuse. He, however, refuses to
accept Lamarck's extreme view as to the origin through effort of
entirely new organs. As he says: "Unfortunately, if Lamarck succeeded in
explaining in a plausible way the modification of organs already
existing, their adaptation to different uses, or even their
disappearance from disuse, in regard to the appearance of new organs he
made hypotheses so venturesome that they led to the momentary
forgetfulness of his other forceful conceptions."[250]

The popular idea of Lamarckism, and which from the first has been
prejudicial to his views, is that an animal may acquire an organ by
simply wishing for or desiring it, or, as his French critics put it, "Un
animal finit toujours par posseder un organe quand il le veut." "Such,"
says Perrier,[251] "is not the idea of Lamarck, who simply attributes
the transformations of species to the stimulating action of external
conditions, construing it under the expression of wants (_besoins_), and
explaining by that word what we now call _adaptations_. Thus the long
neck of the giraffe results from the fact that the animal inhabits a
country where the foliage is situated at the tops of high trees; the
long legs of the wading birds have originated from the fact that these
birds are obliged to seek their food in the water without wetting
themselves," etc. (See p. 350.)

"Many cases," says Perrier, "may be added to-day to tho