States. The bear does not extend so far I think only to Matacumbe- and is probably only a visitor at the time when the turtles lay their eggs, of which he is said to be very fond; there would be little food for him at other times. Key Largo which is connected by a narrow isthmus with the mainland has the mammals of the latter, opossums, squirrels, etc. A burrowing rabbit, according to Colonel Patterson, is found on Rabbit Key, a very small and isolated islet in the bay or sound between the mainland and the keys. To reach Key West from Key Largo, some fifteen or more channels (some of them three or four miles wide) have to be crossed in passing from island to island. The want of fresh water is the probable inducement for the undertaking. The absence of North American mammals from Cuba. and the Bahamas would seem to give a great antiquity to the present course of the Gulf Stream which has proved an impassable barrier. Of birds little can be said on account of their wandering habits. After hurricanes, birds from Cuba are often taken here, which are not seen at other times. A list of the regular breeding birds would be interesting. For the batrachia and reptiles I can only give a list for Key West, kindly made up for me by Mr. Garnian from the collection in the Museum of Comparative Zoology. The batrachia are Hyla cinerea and Scaphiopus solitarius; the snakes, Tropidonotus compressicaudus, Coryphodon constrictor (Tortugas), Elaphis obsoletus and guttatus, Liopeltis æstivus, Crotalus adamanteus; the saurians, Plestiodon quinquelineatum, Cnemidophorus sexlineatus, Anolis principalis, and Sphærodactylus notatus. The chelonians are represented by Thyrosternum Pennsylvanicum; the salt-water terrapin is said to be found at the Marquesas, between Key West and the Tortugas, but I have never seen a specimen. All of these, with the exception of Sphærodactylus, from Cuba, are North American species. The batrachia are said by Wallace to be very seldom represented in insular faunæ, being rapidly killed by salt water. The two species mentioned above I may have been transported with soil from the mainland, which has been sometimes brought to enrich the gardens. Of the insects I cannot speak. There will be probably found here a considerable mixture of North American, Cuban, and 1 While on the subject of mammals I would mention that a very imperfectly known West Indian seal is found occasionally in numbers on the Dog rocks, northeast corner of Salt Key Bank, about one hundred miles from Key West. Bahamian forms, as the distances are not too great to be traversed by most flying insects. It would be an interesting study for an entomologist to find out how far North American species have adapted themselves to the West Indian flora, and how far they have varied under this influence. With regard to the land shells, I am enabled by the kindness of Mr. Thomas Bland, to give more extended lists than in the other departments. Mr. Bland, not content to give me the benefit of his own large stock of knowledge, has spared no pains to gather all the information within reach, principally from Mr. W. G. Binney and Mr. W. W. Calkins. Mr. Binney remarks that the fauna of the keys is quite the same as that of the mainland from Tampa Bay to the Miami River, and that this fauna is about equally derived from the great "Southern Province" of the eastern region of North America and from the West Indies, and gives the following lists in corroboration: : SPECIES CERTAINLY DERIVED FROM THE "SOUTHERN INDIES. WEST INDIAN SPECIES FOUND IN FLORIDA. Zonites Gundlachi, Key West. Patula vortex, mainland and keys. Polygyra Carpenteriana, Key West, Key Helix varians, Key West to Key Biscayne. Polygyra septemvolva, Key West. Glandina truncata, everywhere. Succinea campestris, Key West Biscayne. cereolus, Cylindrella Poeyana, Miami River, Key Macroceranus pontificus,1 Miami River to Macroceranus Gossei, Little Sarasota Bay. Lignus fasciatus, Miami River, Key West. Chondropoma dentatum, Miami River, Cylindrella jejuna, Miami River, Key From Mr. Calkins' list I add P. incana from Key West to Key Biscayne. That some species which are common to some of the West India Islands and to South Florida have had their origin in North America and spread from there, as stated by Mr. Binney, is a fact very difficult to account for. The currents are decidedly against it, and a former connection of the land not confirmed by a study of other classes. We may recapitulate as follows from these notes, imperfect as 1 Key West (Calkins). they are: (1.) The vegetation of the Florida Keys is largely West Indian. (2.) The mammals are entirely North American, and no species common to Florida and West Indies, except perhaps some bats and the manatee, which are not properly attached to the land. (3.) Reptiles and batrachia, North American with only one exception. The Cuban crocodile, lately discovered in South Florida, is never found on the keys. (4.) Land shells are about equally divided, with a slight preponderance of West Indian species. On the whole, therefore, this small region is well entitled to be called a curious instance of intermingling of faunas, and worthy of being carefully studied in all its details, aside from the great interest it presents to the naturalist in its marine fauna and flora, and to the geologist as a working model of many of the agencies by which a large proportion of the sedimentary rocks have been formed. A PROVISIONAL HYPOTHESIS OF PANGENESIS.2 BY W. K. BROOKS. THE HE value of Darwin's Provisional Hypothesis of Pangenesis, as a legitimate attempt at a scientiarinterpretation of the facts of reproduction, is so evident that no apology for endeavoring to discuss the subject is necessary. I venture then to call attention to the following attempt to combine the hypotheses of Owen, Spencer, and Darwin in such a way as to escape the objections to which each is in itself liable, and at the same time to retain all that renders them valuable. All characteristics which are fully established as peculiarities of the species are transmitted through the various forms of asexual reproduction, as well as by the ovum, which has in itself the power to develop, when excited by a proper stimulus which may or may not be the effect of impregnation, into a new individual of the parent form. New characteristics, on the contrary, are transmitted through the agency of gemmules, which are thrown off by the cells implicated in the variation. These gemmules have not, like the ovum, power to develop into a new individual, but reproduce under 1 The comparatively abundant fragments of manatee bones found by me in dredg ing off the Florida coast seem to indicate former migrations of that animal between Cuba and Florida. I believe it is not known now to leave the shores. 2 Abstract of a paper read at the Buffalo meeting of the American Association for the Advancement of Science, August 23, 1876. proper conditions the cell which formed them. They are stored up by the male gland and enter into its excretion, the seminal fluid, and are thus transmitted to the egg by impregnation. Since the body of the female is variable, like that of the male, some of the cells will occasionally form gemmules; some of these may be carried with the fluids of the body to the ovary, and thus gain access to an ovarian egg; but the female differs from the male in having no specialized organ for the aggregation and transmission of gemmules. In this form the hypothesis demands only a very limited number of gemmules at any given time, since only those cells which are undergoing modification give rise to gemmules. We thus escape nearly all the difficulty of the Darwinian form of the hypothesis. We are also able to answer the objection raised by Galton, for the presence of great numbers of gemmules in the blood at any given time is not to be expected, and the testis and seminal receptacle are the only organs which normally contain any considerable number of them from the various parts of the body. According to the new view we are to regard the male element as the originating and the female as the perpetuating factor in the reproductive process. The female is conservative, the male progressive. Adherence to type is brought about through the female, and adaptation to conditions through the male. I will now give a more extended account of the manner in which gemmules are produced. An adult animal or plant is composed of cells which must be regarded as morphological individuals, for they exhibit all the properties which characterize an organism. They absorb nutriment, grow, give rise to formed material, and multiply asexually. These properties they can be proved to possess; we assume that they also have the power to give rise to eggs, or, to use Darwin's word, to gemmules capable of developing into similar cells. Assuming that this power, homologous with that of independent organisms, exists, let us see whether we can learn from the study of independent organisms the conditions under which it may be expected to manifest itself. We know that among animals and plants growth, development, and multiplication are so related that each can go on only at the expense of the others, and that anything which tends to check growth or development favors multiplication; we know too, that asexual and sexual multiplication are related in the same way. If the constituent cells of an organism are organisms in them selves, we should expect them to conform to the same laws. Most of the cells of the body are at any given time very perfectly adapted to the conditions under which they are placed, that is, such an adjustment has been brought about during the process of evolution of the organism, as to place each cell under such relations to its environment as are most favorable to the performance of its function in the body. This state of things will last until some unfavorable change takes place in the environment, either external or internal to the body. The adjustment between the cell thus affected and its conditions will of course be disturbed by the change, and if this change is great enough to check the performance of its normal functions, but not sufficiently great to destroy life, the cell will, after the analogy of other organisms, give birth to gemmules. As these gemmules when transmitted to the next generation are supposed to give rise to variations, we have a simple and consistent explanation of what is without doubt the greatest difficulty of the theory of natural selection: how, among the countless numbers of possible variations, a given cell ever happens to vary at the time change is needed. This explanation is all the more satisfactory since it simply embraces the unicellular organisms which compose the body under laws which are well established as applied to independent organisms. We can also understand why variations do not usually make their appearance in the individuals upon which the new conditions are first brought to bear, but in succeeding generations; for the new conditions do not result in direct variation, but in the production of gemmules which are transmitted to the next generation. It may perhaps be asked why a cell produced from a gemmule should be more variable than one produced by division. A cell formed by division commences its existence as a fully formed cell, but a gemmule has the absorption of food and the building of a body still before it, and it will therefore be more susceptible to external conditions, just as a house in process of construction is more easily altered than one which is finished. If our assumption that newly acquired characteristics are transmitted by the male and those of long standing by the female is correct, the phenomena of crossing should furnish us with a test of the hypothesis. According to the theory of evolution, animals of allied species and varieties are the descendants of a common ancestor, and those characteristics which they have in common are due to this community of descent and are of long |