With proper data as to the force of the waves, the tides, and the soundings around, the extent of the shore platform might be made a subject of calculation. The effect of a windward reef in diminishing the force of the sea is sometimes shewn in the influence of one island on another. A striking instance of this is presented by the northernmost of the Tarawan islands. All the islands of this group are well wooded to windward-the side fronting east, between north and south. But the north side of Taritari is nothing but a bare reef, through a distance of twenty miles, although the south-east reef is a continuous line of verdure. The small island of Makin, just north of Tari-tari, is the breakwater which has protected the reef referred to from the heavier seas. Coral-island accumulations have one advantage over all other shore deposits, owing to the ready agglutination of calcareous grains, as explained in a following page. It has been stated, that coral sand-rocks are forming along the beaches, while the reef-rock is consolidating in the water. A defence of rock against encroachment is thus produced, and is in continual progress. Moreover, the structure built amid the waves will necessarily have the form and condition best fitted for withstanding their action. The little islet of an atoll is therefore more enduring than hills of harder basaltic rocks. Reefs of zoophytic growth but "mock the leaping billows," while other lands of the same height gradually yield to the assaults of the ocean. There are cases, however, of wear from the sea, owing to some change of condition in the island, or in the currents about it, in consequence of which, parts once built up are again carried off. Moreover, those devastating seas which overleap the whole land, may occasion unusual degradation for some parts. Yet these islets have within themselves the source of their own repair, and are secure from all serious injury. The lagoons in coral islands are constantly receiving more or less debris from the reefs; and patches of growing coral within also tend to fill them up. But the effect is slow in its progress, and none but islands of small size, as before stated, shew any approximation to an obliteration of the lagoon. (To be continued.) On the Filaria in the Blood of the Domestic Dog. Messrs Schmitz, Baer, Valentin, Vogt, and Remak, had previously noted the existence of species of Filaria, Monostoma, and Distoma, and of Infusoria, inhabiting the blood of frogs, of certain fishes, and of some molluscs, but no observer had proved the presence of Nematoides living in the blood of animals higher in the zoological scale. We first announced to the Academy, in the course of the year 1843, that we had discovered Entozoa of the genus Filaria living in the blood of certain domestic dogs, and circulating with the globules of that fluid in all the vessels. Since our communication to the Academy, MM. Erdl and Mayer in 1843; Hyrtl Gros, and Ecker, in 1845; Chaussat and Wedl, in 1848; and M. Guérin Méneville, in 1850; have ascertained the presence of Hematozoa in the blood of the field mouse, of the black rat, of several birds and fishes, of the lobster, of the mussel, and of the earth and silk worms. This third memoir, which we have the honour to present to the Academy, comprises the researches to which, for many years, we have devoted ourselves, on the worms living in the blood of certain domestic dogs. We said, in our preceding communications, that this Helminth was a Filaria; and we called your attention to the circumstance that, up to that time, we had not met with this worm save in the microscopic state. Yet in studying this helminth at different ages of the life of the dog, we had proved that in the space of near two years, the microscopic filaria were slowly developed in the blood, and that then the mouth, the digestive canal, and the sexual organs appeared more distinct. And, moreover, that, in three dogs with vermiferous blood, aged from three to ten years, which we had kept several years, whose blood we had examined after death, and dissected the vessels and all the organs, we had never found other than microscopic filaria. Although convinced of the constant existence of these worms along with the globules of the blood in all the red * Vide Comptes Rendus, January 1852. vessels, we had, nevertheless, been unable to account for their origin. We continued our researches, and, after two years of laborious and patient study, we discovered in the blood of a dog with vermiferous blood, which died from the effects of a diet composed exclusively of gelatine, some large worms visible to the naked eye. These entozoa, six in number, of which four were females and two males, were lying in a large blood clot, of recent formation, which filled and dilated the right ventricle of the heart. These helminths were white, filiform, from 14 to 20 centimetres in length, and from one to oneand-a-half centimetres in diameter. We have been able to make out the zoological characters of the male and of the female, to recognise the anatomical disposition of the organs, external and internal,-to study the development of the eggs in the ovaries, and of the embryo in the oviduct, and to convince ourselves that these embryos were identical with the microscopic filaria which we had seen circulating with the blood in all the vessels of several dogs. The blood of the animal in which we found these large worms, itself contained so great a number of microscopic filaria, that we were able to count as many as twelve or fifteen of them in one drop of blood. We observed that the large worms belonged to the genus Filaria, and to the species papillosa, but that these filaria possessed besides some distinctive characters which must inake them be considered as a species still unknown. We propose to give to this Nematoidea the name Filaria papillosa hæmatica canis domestici. Founding on the facts we have just stated, we believe ourselves authorised in concluding, that the large filaria of the blood of the domestic dog lay the eggs of the microscopic filaria in that liquid. These young filaria, up to a certain period of their development, circulate with the blood in all the vessels. It is not until after they have acquired a diameter greater than that of the capillaries that they abide in the heart and the large blood canals. The discovery of these adult filaria had brought us to an important point, but our researches were by no means finished. A crowd of interesting questions still remained for elucidation. The following are the results of our researches: 1st, The number of the microscopic filaria in the blood of certain dogs may be estimated approximately from 11,000 to near 224,000. The mean number in twenty dogs was more than 52,000. 2d, The microscopic filaria, having a less diameter than the globules of the blood, circulate in the smallest capillary vessels through which the globules can pass. One drop of blood taken from the vessels, it matters not in what part of the body, nor in what season of the year, contains these little Hematozoa. 3d, The chyle and the lymph of the dogs whose blood contains microscopic filaria, even in very great number, do not contain any of these worms. 4th, The normal liquid secretions, such as the saliva, the bile, the pancreatic juice, the urine, the spermatic fluid, the serosity of the great serous membranes, as well as the fluids abnormally secreted, do not contain any of these minute animals. 5th, Twenty-eight dogs with vermiferous blood, of different kinds and ages, kept, some during several months, others during more than five years, animals which had approximately from 11,000 to near 224,000 microscopic filaria in their blood, have been dissected in the course of the winter, the spring, the summer, and the autumn, with the greatest care, without a single filaria, invisible or visible to the naked eye, having been perceived in the different tissues. We think, then, we are able to affirm, that the filaria of the dog, whether microscopic or of from 14 to 20 centimetres in length, and near 1 millimetre in diameter, or of the size of a thick thread, lives exclusively in the blood during all seasons of the year, draws nourishment from that fluid, and never abandons it. 6th, The frequency and the rarity of dogs having vermiferous blood, and of those without it, calculated from 480 dogs, the blood of which has been examined, is, in the mean proportion, one dog with vermiferous blood to twenty or twenty-five without it. 7th, Vermiferous blood occurs more frequently in old and adult dogs than in young. 8th, These worms appear in the blood of dogs without distinction of kind or of sex, and whatever be the state of leanness, of fatness, of health and of disease, of these animals. 9th, The microscopic filaria, even when present in the approximate number of near 224,000, do not alter the instinctive faculties of the dogs, and do not at all weaken the muscular energy of these animals. 10th, The vermiferous blood of the dogs presents no very notable modifications in its physical characters, and in the proportionate weight of its organic and inorganic principles. 11th, The microscopic hematozoa transfused with from 150 to 300 grammes of a liqueur globuleuse defibrinæ into the vessels of nine dogs, whose blood contained no worms, disappeared from their blood in from the eighth to the fortieth day. The dogs were killed, and the filaria were neither found in the fluid secretions, nor in the tissues, nor in the different cavities. 12th, In two dogs, differing in kind and age, having no filaria in their blood, into whose vessels from 200 to 800 grammes of vermiferous defibrinised blood were ejected, the filaria have continued to live in the blood during more than three years, or up to their natural death. When opened and dissected these dogs have not presented any filaria save in their blood. 13th, The microscopic hematozoa of the blood of the dog transfused with the liqueur globuleuse defibrina into the vessels of two rabbits, have continued to live in the blood of one of them during eighty-nine days, after which time the filaria disappeared from the blood. At the autopsy of this rabbit the filaria were not found again in the tissues. 14th, The microscopic filaria transfused with the defibrinised liquor which we have mentioned into the blood of six adult frogs, two of which already had filaria in their blood, continued to live in the vital fluid of these animals during eight days, or during the time the globules of the dog's blood appeared unchanged among the globules of the frog's blood. On the ninth and tenth day, the globules of the dog's blood being altered, the microscopic filaria injected with it disappeared, and the eight frogs died of a scorbutic disease. These transfusions then demonstrate that the microscopic filarious blood cannot continue to live, either in the blood of |