Imágenes de páginas

ulars concerning these Medusa-like forms, which he proposed to embody in a paper to be presented at a future meeting.

Professor W. B. Rogers made a communication on the subject of binocular vision, giving his own explanation of the phenomenon, and illustrating it by the aid of the stereoscope.

This communication was followed by remarks, from Professor Agassiz, Dr. Pickering, Dr. W. F. Channing, and the President, on various phenomena connected with the laws of vision.

Dr. Durkee exhibited filterings from the water of a lake in Haverhill, showing animal forms containing oil, similar to those found in Cochituate water at the present time.

Four hundred and eleventh meeting.

February 13, 1855. — MONTHLY MEETING. The PRESIDENT in the chair.

Mr. G. P. Bond presented, in behalf of W. H. Emory of the U. S. Topographical Engineers, a paper, entitled,

" Discussion of Observations for the Isodynamic, Isogonic, and Isoclinal Curves of Terrestrial Magnetism on and near the Line of the Boundary Survey between the United States and Mexico, made in 1849, 1850, 1851, and 1852, under the Orders of Major W. H. Emory, Astronomer of the Boundary Commission,” — being a continuation of the article on the same subject in Volume V., page 1, of the Academy's Memoirs.

Mr. Bond also exhibited some diagrams of the planet Saturn, and mentioned various facts concerning it; namely, that the inner edge of the rings is constantly approaching the planet itself; that the ball is seen through the rings, which are consequently transparent; that the color is different in different parts of the rings, the equatorial regions being white, the temperate region reddish, and the polar bluish. He also mentioned that the shadow of the ball upon the ring can be seen on both sides of it, being on one side rather faint, but on the other quite decided. This anomalous appearance he first noticed in October, 1852, and as yet he could give no satisfactory explanation of it, nor of the singular shape of the shadow, the convexity of which was towards the ball, instead of from it, as it might be expected to be. His observations were made with the great Cambridge Refractor in the years 1852, 1854, and 1855.

Four hundred and twelfth meeting.

March 13, 1855. — MONTHLY MEETING. The PRESIDENT in the chair.

Professor Lovering alluded to the fact, that at a previous meeting the opinion of Arago had been referred to as favorable to making the subject of “ Table-moving," so called, a matter of scientific investigation. Since that meeting he had himself examined the new edition of Arago's complete works, and had found nothing to justify such a conclusion; on the contrary, he found that Arago declared himself satisfied that the appearances in question are founded in imposture.

Four hundred and thirteenth meeting.

April 10, 1855. — Monthly Meeting. The PRESIDENT in the chair.

After the record of the preceding meeting was read and approved, Professor Agassiz confirmed from his own knowledge the statement of Professor Lovering at the preceding meeting concerning Arago's opinions of the so-called “Spiritual Manifestations.” And yet, he said, notwithstanding the unanimous opinion of the committee of the French Academy, to which the subject had been referred, that the whole thing is a matter of imposture, the authority of that learned body and that great philosopher is constantly appealed to as favorable to the alleged reality of the appearances in question.

Professor Agassiz made a communication on the subject of the classification of Polyps. He remarked that Cuvier included under Polypi what are now known as Hydroids and Bryozoa. Milne-Edwards has demonstrated that the latter are not Polypi, — their structure not being truly radiate, — but the lowest order of Mollusks, and he called them Molluscoids. Polypi and Hydroids, however, are still grouped together. By Ehrenberg these are called Anthozoa, — which he divides, further, into two groups: Zoöcoralia those which are free, and Phytocoralia, those which are attached; but under these groups he has made a very unnatural distribution of the families, as the young and adult of the same species may differ in this re

spect, the young being sometimes attached, when the adult • is free. Professor Agassiz exhibited in illustration a specimen of Manicina areolata from Florida, the young of which are sessile, whilst the adults are free. Milne-Edwards subdivided Polypi into Actinoids, Alcyonoids, and Sertularians, which he considers as coequal groups, a division chiefly based on the character of the tentacles and calycle ; but Professor J. D. Dana has at last shown that the first two form one natural group, and the Sertularians another, thus for the first time uniting the types of the class of Polyps together into one division. Professor Agassiz is however of opinion, that the Hydroids should be removed from the class of Polypi, and referred to that of Acalephæ. They are pedunculated Medusæ in the same sense that Crinoids are pedunculated Asteroids. The true Polypi are divided by Dana into two orders, the Actinarians and Alcyonoids. Professor Agassiz thinks he has detected indications of superiority and inferiority of structure between these orders, founded on the structure and number of the tentacles, &c. Thus in Alcyonoids these are fringed and definite in number and position, being two in the long axis, and in three pairs on the sides, while in Actinoids they are simple, and there is not the same regularity of number and position. The former should therefore be regarded as ranking higher than the latter. Among Actinoid Polyps some are simple, while others are compound individuals. The former would at first seem to stand highest in the scale, whereas they

are in reality the lowest, as their tentacles are indefinite in number. Among the Actinoids there are species provided at first with one mouth, which afterwards contracts and divides into two, each being surrounded by its row of tentacles, the animal being thus double above, but single below; and the division may be repeated, so that the number of mouths shall be four, belonging apparently to as many individuals, while in reality they are but one, being united below. The multiplication is indefinite in many types. Such a peculiar structure naturally leads to the question, What defines the individual in this case, — the possession of a single mouth, or the union of all the branches below? In Meandrina a number of mouths are surrounded by a single row of tentacles, and there is one common digestive cavity. In a Madrepore, which has sprung from a single egg, the main polyp may preserve its position at the top of the stem, while buds are pushed out from the stem, constituting a community of individuals subordinate to the principal one. This shows distinctly that polyp communities are combining into higher unities. Among some of the Alcyonoids, as in Renilla, Pennatela, &c., a community of individuals based upon a single stem, each polyp being provided with its own set of tentacles, and all communicating with a common cavity, has the power of changing its position and moving about freely, exhibiting a new kind of individuality, a community moving as a single individual. Among the Polypi, then, the compound individual presents the higher type, and Alcyonoids, which are all compound animals, are higher than Actinoids, among which alone simple polyps are found. This position accords with the revelations of geology, the former never occurring as fossils in ancient formations, while the latter have built up all the coral formations of past geological epochs. Dana has shown that the Actinoids bud in two ways, some dividing at the top, others budding laterally. Professor Agassiz regards the Madrepores as the highest, on account of their tentacles being definite in number, and some preserving a top animal ; next he places the top budders (Asteroids), while those that bud laterally (the Caryophyllians) rank lowest. This order of arrangement corresponds in general to the geological succession of Polypi from the lowest formations upward. Again, every coral reef rising from the bottom of the ocean shows in its various stages a succession of species reminding us of the same general plan.

Professor Agassiz remarked, that the study of this class of animals is greatly embarrassed by difficulties growing out of the fact, that the general features vary much in communities of the same species, so that these features cannot be so much depended upon for characters as the intimate structure of the individual polyps. He was inclined to believe that many of the genera of this class recently described by naturalists are based on evanescent characters, in fact upon different stages of development of well-known types.

Dr. A. A. Hayes called the attention of the Academy to a new species of wax, a specimen of which was on the table, and made the following remarks:

“ The commercial relations of our country, extending along the rivers of South America, are making known to us the products of the vast forests of the interior, many of which have a high value in the arts and are new to commerce. Among specimens received by me is the peculiar wax before us, respecting the origin of which I possess only a meagre amount of information. It is obtained by boiling the deep green leaves of a shrub resembling laurel, abounding in the forests back from Para and Bahia, and is used to some extent as a substitute for wax in the manufacture of candles.'

“ This wax has a light tint of greenish-yellow color, transmitting nearly white light through thin portions ; it is hard, the angles of the fragments scratching gypsum. Its fracture is slightly conchoidal, lustre more dull than that of ordinary wax. By rubbing, it becomes electrically excited, and takes and retains a fine polish; it is brittle, without softening when compressed between the fingers.

“The average sp. gr., determined on many specimens, is at 60° F. 1.000, or the same as distilled water. When heated to 120° F. for some time, it loses moisture, and exhales a pleasant balsamic odor, not unlike that of pinks.

« AnteriorContinuar »