CRYSTALS of unorganised matter are spoken of as symmetrical. The symmetry, however, which they exhibit is not .a bilateral sym metry. It consists of the repetition of the same angles and facets at the poles of an axis, but the repetitions are not reverses. The reader may illustrate my meaning by cut ting a rhomboid in paper, when he will observe that each of its angles and sides are twice re peated, but he will find it impossible to fold it so that one half shall coincide with the other.
The precise import of the symmetry of or ganised bodies is, as repeatedly indicated above, as yet involved in mystery. Albeit a fact so evident, so constantly obvious to our senses, as often, like gravitation, to pass unheeded, it is a great and an important fact, — a fact of the same order with those which have already led to the establishment and demonstration of grand, comprehensive, and unassailable theo ries—the bright triumphs of the human intel lect, that have reduced to order, simplicity, and connexion, what before was all confused, complicated, and disjointed, — a fact, there fore, that inspires us with hope for our, as yet, imperfect science of anatomy. It seems
to tell of radiant forces, of certain, definite, mathematical, and inexorable laws, concerned in the production of animals. Taken with the other important fact — serial homology, it seems to suggest for the development of Vertebrata and Articulata the multiplica tion of centres in a serial line—of centres of radiant force, that then proceed to in duce the surrounding particles to arrange themselves in a symmetrical figure. In truth, as the mind contemplates this fact, various theories pass before it, yet shadowy, change able, and indistinct as a phantasmagoria. One day, perhaps, some one of these shall meet with definite enunciation and clear demon stration ; at present we must be content with putting the fact of symmetry prominently forward and exhibiting it in various points of view, with declaring it an important fact, and not a matter of course.
(S. R. Pittard.)