Зображення сторінки
PDF
ePub

our present knowledge; the absence of the vertebrated classes in the lowest strata being based upon strong negative evidence. Of course it is possible that the Vertebrata may have existed, from the earliest creation of life, upon the earth; yet not only have the most rigorous researches of many years failed to discover a trace of their remains, but, judging from the gradual development or substitution of the vertebrated classes through so many phases, until they assume such importance in the Mammalia of the Cainozoic period, the conclusion that such high types of life were altogether absent during the first great life epoch appears strongly confirmed. Notwithstanding the careful search that is constantly in operation, several years have now elapsed without developing any new facts of importance tending to lower the range of classes. The longer it continues we may the more safely begin to trust the value of our conclusions, and to assume that time will give them the character of truth.

In conclusion, we find the remains of the earliest organic body that we are acquainted with is a Bryozoon.* perhaps associated with Annelids. If these were the first creatures that ever existed upon the earth, how interesting to look upon their remains, and to find that they are by no means the lowest animals in the scale of organization. But have we really found such ?-or is it one of the first traces of the spread of life from some distant cen where the first creation unveiled itself in many classes, perhaps even the entire invertebrata with which we become acquainted as we ascend the Silurian system; the epoch that undoubtedly is the first great life era that we can separate in geological sequence. After the Bryozoa and Annelida, the first or lowest classes observed, are Zoophyta, Crustacea, and Brachiopoda ; and so far as

Oldhamia radiata.

a

we are able to ascertain, these composed the most ancient Fauna of the ocean. They were soon afterwards followed by the Cephalopoda, and many other classes. The only class of comparatively recent introduction is Cirrhipedia. The sessile Cirrhipedes are only found in Cainozoic strata, becoming so abundant towards its close, and now so universally spread over the world that the present time might be styled the "Age of Cirrhipedes." *

The first evidence of the vertebrata, in the upper Silurian, has been already adverted to in the occurrence of Placoid Fishes, in the Ludlow Shales. The earliest Reptiles in the Devonian and Carboniferous systems shew how long that class existed before it arrived at its maximum in the Mesozoic period. The first trace of Birds seems indicated by their footprints in the Trias, though the earliest undoubted examples are in Wealden and Eocene strata. The first Mammals appear in the Inferior Oolite, more frequently in the Wealden; their present importance in the economy of nature being coincident with the commencement of the Cainozoic period, in every region where such strata have been identified. With the accumulated observations of geologists to rely upon, and the very general manner the subject has been treated, I hope to have correctly placed it before you, The object has been to shew a correct tabulation of facts, and their relation, according to the present state of our information.

* Darwin.

THIRTEENTH ORDINARY MEETING.

ROYAL INSTITUTION, 3rd May, 1858.

DR. INMAN, PRESIDENT, in the Chair.

The Rev. H. H. Higgins exhibited Corundum from Asia Minor and Naxes, and observed that, owing to the high price of the mineral, efforts were being used to obtain it for commercial purposes from the coast of Coromandel.

Dr. EDWARDS exhibited some specimens of aluminum and other substances in the amorphous form, likewise the silicate of soda; observing, with regard to the last, that it would probably come into very general use for important purposes.

Thus it might render garments uninflammable; would by its detergent qualities become a useful ingredient in soap; was serviceable in frescopainting, sizing of calicoes, and as an adhesive cement, where hot water did not come in contact with it.

Mr. Cocker's new patent Wire-guage was shewn and explained.

The paper for the evening was then read :

ON REARING MACRO-LEPIDOPTERA.

BY JAMES FITZHERBERT BROCHOLES, Esq. In order to make this paper the more thoroughly understood, it may be well here to explain, or rather define, the term Macro-Lepidoptera.

Entomologists divide butterflies and moths into two sections, under the titles Macro-Lepidoptera and MicroLepidoptera.

The former comprises the first five tribes, namely, the Rhopalocera or Butterflies, the Sphinges, the Bombyces, Nocture, and Geometræ. Though some of the species included in these are small, the majority are large.

The latter section comprises the Pyrales, Crambinæ, Tortrices, Tineinæ, and Pterophoridæ. In these tribes a few of the species are moderately large, but the majority are small.

To go out and collect a number of larvæ, without previously providing suitable places for them at home, would be folly; a few remarks about breeding-cages will, therefore, not be out of place.

A large box, measuring half a yard or two feet square, will be very useful; especially for those insects which spin cocoons or webs, and for such as remain only a short time in pupæ. The box should be constructed on the plan of a meat-safe, the sides and top being of fine wire gauze, nailed tightly on a frame-work of wood. It is immaterial whether the top or a side be the doorway, provided a full view of the whole interior can be obtained. Moss should be placed in the bottom, to the depth of several inches, for the caterpillars to bury themselves in when about to become pupæ; and there should also be a fair quantity of ledges and corners throughout the box, to form asylums for the web-spinners and others which do not bury. The wooden bottom of the cage absorbs much of the moisture from the moss, whilst there is a constant drainage from the surface by means of evaporation through the wire gauze on the sides and top; hence, a dryness ensues which is very prejudicial both to larvæ and pupæ. This must be obviated by frequent waterings. On the other hand, too much moisture is equally injurious and care should be taken to preserve a medium. Should the box be allowed frequently to become quite dry, waterings cause it to grow mouldy, and the insects die; hence, it is necessary to keep it as much as possible equally moist.

For those species which spend the winter, or any lengthened portion of the summer in the pupa state, either under ground or amongst moss, &c., the following is an admirable cage: Take a large flower-pot and fill it onethird full of fresh, sweet moss, then place it upon a soup-plate full of water, and tie book-muslin over it.

The evaporation of the water, passing through the hole in the bottom of the pot, keeps the moisture in the moss nearly at the right point, so that the trouble of frequent waterings is obviated; but an occasional one is nevertheless advantageous. A number of flower-pots, fitted up in this way, enable the entomologist to keep each species of larvæ separate; to treat each as it requires; to watch each through its several transformations; and to arrive at conclusions more readily than he could do by keeping all in one large box. The pots also may be kept either in or out of doors; whereas, a box would soon be flooded, and the larvæ and pupæ drowned, if kept where rain has access.

The box, moreover, would soon be destroyed.

When the cages are tenanted by larvæ, care should be taken to keep them airy, sweet, and clean, otherwise diseases are generated which prove fatal to the moths in one or other of their stages. When many caterpillars have been reared in one cage it necessarily becomes charged with refuse, so that, when the insects are all hatched, fresh moss should be substituted for the old, taking care, of course, that no good pupa are thrown away in the change.

It sometimes happens that individual specimens remain in the pupa state for some time after the majority have flown, and odd ones of good species are valuable.

Such domiciles are alone necessary for the rearing of

« НазадПродовжити »