Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/831

 F R F R 795 tion cannot but affect the thoughts and ultimately the practice of all teachers who will be at the pains to under stand it. Froebcl s own works are 1. Mcnschenerziehung (there is a French translation by the Baronne de Crombrugghe) ; 2. Pddagogik d. Kindergartens; 3. Kleincre Schriftcn, herausgegeben von Wichard Lange ; and 4. Mutter- imd Koselicdcr. We have a lengthy but unsatisfactory life in A. B. Hanschmann s Friedrich Frubcl. An unpretentious but useful little book is F. Frocbel, a Biographical Sketch, by Matilda H. Kriege, New York (Steiger). A very good account of Froebel s life and thoughts is given in Karl Schmidt s Gcschichtc d. Pddacjogik, vol. iv. ; also in Adalbert &quot;Weber s Gcschichtc d. Volksschulpad. u. d. Kleinkindcrerziehung (Weber carefully gives authorities). For a less favourable account see K. S track s Gcschichtc d. dcutsch. Volksschulwcscns. The article &quot; Frb bel &quot; in K. A. Schmid s EncykloptidiG is by Ueinhardt. Frau von Marenholtz-Bulow has published her Erinncrungcn an F. Frobcl (a book which has been translated by Mrs Horace Mann). This lady, who has been the chief interpreter of Froebel, has expounded his principles in Das Kind u. sein Wcsen, and Die Arleit u. die ncuc Erzichung. In England Miss E. Shirrelf has published Prin ciples of Froebel s System, and a short sketch of Froebel s life. The late Joseph Payne advocated Froebelism in a pamphlet, Frocbel and the Kindergarten System ; also in the book published since his death, A Visit to German Schools. In the United States, Miss E. E. Peabody, who has taken an active part in the spread of Froebel ism, has written Moral Culture of Infancy (New York). VV. N. Hailman treats of Froebel in his Lectures and his Kindergarten Culture (Cincinnati). A. Kohler s Praxis is the best known German work on the Kindergarten (it is translated as Kindergarten Educa tion, New York) ; and T. F. Jacobs s Manuel is the best in French. (R. H. Q.) FROG, the common name of an extensive group of Batrachians forming, along with the toads, the amphibian order Anoura. They are divided into 9 families, containing 92 genera and 440 species, and are found in all quarters of the globe, being most abundant in the tropical and sub tropical regions, but also occurring within the Arctic circle. Most of the families have a very limited distribution, and only two of them, the true frogs (Banidce), of which there are 150 species, and the Polypedatidce, a family of tree-frogs containing 124 species, can be regarded as almost cosmopo litan. The neotropical or South American region is richest in peculiar forms, while it possesses some only found beyond it in tin widely remote Australian region ; thus the Pelodry- adtf, a family of tree-frogs, is peculiar to the two; the genus Liforia is confined to Australia, with the exception of a single species occurring in Paraguay ; while the only frog known in New Zealand has its nearest allies in South America. Those regions bear also a negative resemblance in the total absence from both of the genus JSana, the 60 spocies of which are distributed throughout the other quarters of the globe. These facts, among others, have been adduced in support of the theory that at one time the continents of South America and Australia had a land connexion. Frogs are almost totally absent from oceanic islands, a single species (Liopelma Hochstetteri) occurring in New Zealand, and one or two others in the Pacific islands, as far east as the Fijis, beyond which they are unknown. On the as sumption that those islands obtained their present fauna from the nearest continental land, the absence of frogs can be readily explained by the fact that salt water is alike fatal to the adult frog and to its spawn, and thus formed an insuperable barrier to their migration. Frogs, as is shown by their wide distribution, are capable of enduring a considerable degree of both heat and cold ; they are, however, altogether intolerant of long-continued drought, a desert forming as certain a barrier to their migra tion as an ocean. Both during their larval stage and after wards, for the purpose of cutaneous respiration, abundant moisture is a necessity of their existence; consequently, whether they live on the ground or on trees, they are never found far from rivers, marshes, or lakes. In winter the frogs of northern climates hibernate, burying themselves in the mud at the bottom of pools, and lying clustered together in a state of complete torpidity. In hot climates they are said to go into a similar condition, known as &quot; aestivation,&quot; during periods of exceptional heat and drought, in order to retard the dissipation of the moisture in their bodies. On reappearing from their long winter sleep the work of repro duction is at once entered upon, the males making their presence known to the females by the vigorous exercise of their vocal organs. The croaking of the common frog can only be regarded as pleasant from its association with the welcome advent of spring ; still more unpleasant, however, is the much louder croak of the edible frog of the Continent, the species to which Horace probably refers in the lines &quot; ranwque palustres Avert unt sonmos.&quot; The eggs of the frog, consisting of little black specks sur rounded by an albuminous envelope, are fertilized during their extrusion from the body of the female, and are gen erally deposited at the bottom of the water, ascending, how ever, soon after to the surface, owing to the swelling and partial decomposition of the glairy substance surrounding the ova. There are several species known in which the eggs are deposited in an exceptional manner. Those of a small frog (Alt/tes obstetricans) found in France and Germany form a long chain, which the male twines round his thighs, retiring with them into seclusion until the young are ready to leave, when he enters the water, and the tad poles immediately make their escape. The female of an American tree-frog (Nototrema marsiqriatiim) has a pouch along the whole extent of its back for the reception of its eggs ; and Professor Peters of Berlin has recently drawn attention to a tree-frog of the genus Polypcdates found in tropical West Africa, in which the female, after depositing her eggs in the usual mass of albuminous jelly, attaches them to the leaves of trees overhanging a dry water-hole or pool. The albumen speedily dries and forms a horny coating on the leaf, under which lie the unimpregnated eggs. On the advent of the rainy season the albumen becomes softened, and the eggs are washed into the pool below, now filled with water, where they are fecundated by the male. The development of the egg after impregnation proceeds more or less rapidly according to the temperature, the young of the common frog being hatched, according to llusconi, in 4 days, in a temperature varying from 70 to 80 Fahr., while in the climate of England this does not take place in less than a month. The creature which emerges from the egg is altogether unlike a frog, consisting mainly of a bulky head and tail, and wholly destitute of limbs. This is the tadpole or larval stage in the development of the frog, when it is essentially a fish, capable only of exist ing in water, breathing by gills, and having like a fish a two- chambered heart. At first the gills or branchiae are ex ternal, but they are soon withdrawn within the branchial cavity, and concealed by an opercular membrane. As the process of development proceeds, the limbs begin to bud forth, the posterior pair appearing first ; and with their growth the tail begins to dwindle, not falling off, but being gradually absorbed. At the same time vast changes are taking place in the blood-vascular system, the gills gradually disappearing, two lungs being developed, and the heart be coming three-chambered as in reptiles. The young frog must now come to the surface to breathe, and soon leaves the water altogether. On emerging from the egg, the tad pole at first feeds upon the gelatinous mass which before had formed a protective covering. It is unprovided with teeth, but has two minute horny jaws, which enable it to feed on decaying animal and vegetable matter. According to Bell (British Reptiles), tadpoles sometimes kill and feed upon each other. &quot; I observed,&quot; he says, &quot; that almost as soon as one had acquired its limbs it was found dead at the buttoin of the water, and the remaining tadpoles feeding