PROGRESS OF PUBLICATION.
THE series of popular zoological works by YARRELL and BELL has received a very interesting and important addition, in a simi- lar one on animal physiology as ;applied to classification, by Pro- fessor JONES of King's College, entitled .1 General Outline of the Animal Kingdom. People are pretty well acquainted the appearance and peculiar formation and habits of indivi- dual animals; but of their leading generic characteristics, by which they are divided into distinct classes—of comparative ana- 'omy in a word —they are uninformed : it is reserved for tie scientific naturalist to take such a comprehensive and enlightened view of the animal creation.
Mr. JONES adopts CUVIER'S classification, of course ; rearrang- ing, however, the miscellaneous mass of creatures, the lowest in the scale of animated nature, that CUVIER has lumped together indiscriminately under the head Zuiiphytes, or Radiated Animals. These are subdivided into two separate groups, each distinguished by essential differences of the nervous system ; but requiring microscopic investigation and the most minute and patient observa- tion of their organization and economy to discern their character- istics. To Mr. OWEN science is indebted for one division, namely Nematoneurose, or Thread-nerved—in which nervous filaments are visible ; and to Mr. M.LEAY for another, called Acrita—having no distinct nervous organization whatever. These last form as it were the connecting link between the animal and vegetable kingdoms ; and include Sponges, and the lowest order of Polyps, which are the subjects of description in the First Part. The dried sponge that we use is only the skeleton of the multitu- dinous animal ; whose vital part consists of "a thin film of glairy, semifluid matter, composed of aggregated transparent glo- bules," coating every filament; these filaments being moreover tubular. Here is a description of the living sponge— "On placing a living sponge of small size in a watch-glassIbr small glass trough filled with sea-water, and watching it attentively, something like a vital action becomes apparent. The entire surface is seen to be perforated by innumerable pores and apertures, some exceedingly minute, opening on every part of its peri- phery ; others of larger dimensions, placed at intervals, and generally ele- vated upon prominent portions of the sponge. Through the smaller orates the surrounding water is continually sucked as it were into the interior of the spongy mass, and it RS constantly flows out in continuous streams through the
larger openings. • • The entering fluid rushes in at the count. less pores which occupy the body of the sponge ; but, in its progress through the canals in the interior, becomes directed into snore capacious channels, com- municating with the prominent larger orifices, through which it is ultimately ejected in equable and ceaseless currents. Organized particles, which neces- sarily abound in the water of the ocean, are thus introduced into the sponge on all stiles, and are probably employed as nutriment, whilst the superfluous or effete matter is continually cast out with the ,issuing streams as they rush through the fecal orifices."
THE BIRTH OF A SPONGE.
" At certain ',seasons of the year, if a living sponge be cut to pieces, the channels in its interior are found to have their walls studded with yellowish gelatinous granules, developed in the living parenchyma which lines them; these granules are the germs or gemmules from which a future race will spring ; they seem to be formed indifferently in all parts of the mass, sprouting as it were from the albuminous crust which coats the skeleton, without the appear- ance of any organs appropriated to their development. As they increase in size, they are found to project more and more into the canals which ramify through the sponge, and to be provided with an apparatus of locomotion of a description which we shall frequently have occasion to mention. The gernmule assumes an ovoid form, and a large portion of its surface becomes covered with innumerable vibrating hairs or cilia,a8 they are denominated, which are of in- conceivable minuteness, yet individually capable of exercising rapid movements, which produce currents in the surrounding fluid. Assuan therefore as a gen-mule is sufficiently mature, it becomes detached from the aides where it was formed, and, whirled along by the issuing streams which are expelled through the fecal orifices of the parent, it escapes into the water around. Instead, however, of falling to the bottom, as so apparently helpless a particle of jelly might be ex- pected to do, the ceaseless vibration of the cilia upon its surface propels it rapidly along, until, beiag removed to a considerable distance from its orig:.nal, it attaches itself to a proper object, and, losing the locomotive cilia which at at first possessed, it becomes fixed and motionless, aud develops within its sub- stance the skeleton peculiar to its species, exhibiting by degrees the form of the individual flow which it sprung. It is curious to observe this remarkable ex • ception which sponges exhibit to the usual phenomena witnessed in the repro- duction of animals, the object of which is evident, as the result is admirable.
The parent sponge, deprived of all power of movement, would obviously be incapable of dispersing to a distance the numerous progeny which it furnishes ; they must inevitably have accumulated in the immediate vicinity of their place of birth, without the possibility of their distribution to other localities. The seeds of vegetables, sometimes winged and plumed for the purpose, are blown about by the winds, or transported by various agencies to distant places ; but, in the present instance, the still waters in which sponges grow would not have served to transport their progeny elsewhere, and germs so soft and delicate could hardly be removed by other creatures. Instead therefore of being help- less at their birth, the young sponges can, by means of their cilia, row them- selves about at pleasure, and enjoy for a period powers of locomotion denied to their adult state."
The Polyps, including the Corals and the Actinia, called sea- flowers, that are found in puddles on the sea-beach, and devour muscles and small crabs, are a still more curious and interesting group of animals.
The numerous diagrams illustrating the descriptions, make the organization of these animalculze as clearly intelligible as the anatomy of an elephant ; and excite anew our admiring wonder at the endless variety of structure in the animal creation, and the extraordinary completeness and minuteness of the provisions for the nutrition and reproduction of every class of creatures.
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