he gives the forms of the spores, though not always accurately, and their measurements. While the Italian and German writers on the one hand tend to too great a subdivision of genera and species, Nylander, on the other, is frequently too comprehensive, though this is perhaps the safer error of the two.

Professor Tuckerman of Amherst, has expressed briefly his views on the value of spore characters, in his "Lichens of California," 1866, and has laid the foundation of a more sound and instructive doctrine on this subject than previous writers. In his opinion, which has been followed in what precedes, "less weight than has often been assumed should be given to spore differences of a merely gradal character, or such others as depend only on mensuration, and more to those that seem typical." He considers that there are "two well defined kinds of lichen-spores, complemented in the highest tribe only by a well-defined intermediate one. In one of these (typically colorless) the originally simple spore, passing through a series of modifications, always in one direction, and tending constantly to elongation, affords at length the acicular type. To this is opposed (most frequently but not exclusively in the lower tribes, and even possibly anticipated by the polar-bilocular sub-type in Parmeliacei), a second (typically colored) in which the simple spore, completing another series of changes, tending rather to distension and to division in one direction, exhibits finally the muriform type." In accordance with this view Rinodina is distinguished from Lecanora, and Buellia from Lecidea. Theloschistes parietinus is separated from Physcia, a genus with colored spores, and placed in a distinct genus, the type of whose spore is the polar-bilocular. On the other hand Biatora rubella would not be separated from that genus, which includes species with simple spores, merely on account of its septate spores, nor Buellia petræa placed in a distinct genus, Rhizocarpon, on account of its muriform spores, nor Lecanora cervina on account of its polysporous

spore-cases. It is to be observed, however, that the typically colored spore is often, as Professor Tuckerman expresses it, decolorate. Thus the spores of Buellia petræa, are often, and always, so far as I have observed, in a form which occurs on rails, colorless, and frequently only 2-blastish. Similar conditions also occur of Rinodina sophodes and R. ascociscana. Pertusaria is another genus in which the spores should probably be considered as typically colored. They are usually of a yellowish tinge, and in one specimen of P. leioplaca they were of a rich golden brown. There are many genera in which species with spores belonging to the typically colored series, have spores always, so far as observed, colorless, or "decolorate." In the genera of all the great families of lichens will be found spores corresponding to these various types; and a table might be constructed, showing the analogies throughout. But into the subject of lichen classification it is not my purpose here to enter.

Our illustrations in the preceding number of the NATURALIST show the different types of spores as thus distinguished; those of T. parietina being polar-bilocular, those of Biatora rubella, acicular, and those of Buellia petræa, muriform. The adoption of this idea will certainly introduce an order and clearness into lichenology which it has hitherto lacked, and will do away with a host of genera of the German and Italian writers, which serve only to encumber the books and to embarrass and confuse the student. There are perhaps some exceptions, as Professor Tuckerman admits, in regard to Gyalecta, and as is perhaps the case also with Arthonia. But these may disappear with further knowledge, and we have to thank the Professor for an idea which greatly simplifies a difficult study, and whose advantages, as he justly remarks, far outweigh its difficulties. He has promised a further discussion of the subject in his forthcoming work on the Genera of North American Lichens.

THE SPERM WHALES, GIANT AND PYGMY.

BY THEODORE GILL, M.D., PH.D.

Vastness of size is so generally, and it may almost be conceded, so naturally associated in the popular idea with the whales, that some may scarcely be able to realize at first the fact that there are species no larger than ordinary porpoises; and yet which agree so closely in all the more essential elements of structure with some of the whales, that it is impossible, in a natural system, to separate them far from their gigantic relatives. We say some of the whales, for it is to be observed that the animals which are designated popularly as whales do not form a natural group, as contradistinguished from other animals. As popularly applied, the word whale is a designation used in common for all the gigantic cetaceans, whether they be toothless and furnished with whalebone, as are the right-whales, or whether they be toothed, as are the sperm-whales, or cachalots.*

The pygmies, to which we have alluded above, would not answer, then, to the popular conception. But, indeed, there are no characters which are coördinated with size, and which would enable one to give a definition other than relative to size. We have to enter upon a more profound examination before being able to ascertain the relations of the various members of the cetacean order. It is only by taking into account the sum total of characters, internal as well as external, that we are at length enabled to arrive at a correct appreciation of the true affinities of animals, and this inductive mode of study, applied to the cetaceans, teaches us that

It should be added, however, that "whale" seems to be used by some whalemen as a quasi-generic term for the cetaceans (see Cheever, "The Whale and his Captors," pp. 96, 97), and is also applied by other persons to some of the larger Delphinidæ, such as Beluga (the white whale), Orcu (the killer whale), Globiocephalus (the caing whale), etc.

in the order are two great groups, which, we may at once add, are suborders; and that these groups are distinguished from each other by numerous characteristics: the most apparent of these are, in one group, (the MYSTICETE,) the development of whalebone on the roof of the mouth, and the entire want of teeth,*-they being reabsorbed into the gums before birth, the development of an olfactory organ, and of nasal bones free at their distal ends; and in the other group, (the DENTICETI,) the absence of the whalebone, and the development of teeth after birth generally persistent in one or both jaws during life, but in some forms more or less early deciduous; the olfactory organ is atrophied, and the nasal bones are appressed to the frontals and overlapped by the vomer.

It is not in one alone of these groups that we find associated together, in a natural morphological combination, giants and dwarfs, although only in one do we find the contrast in the present age of our globe. It is the family of Physeterida (the sperm-whales) which furnishes us with the contrast in living forms; only giants are now living to represent the Balanide (the right-whales), and Balaenopterida (the fin-back whales), but in the miocene age, a species of a fin-back whale lived that when adult was not even as large as the new born young of the fin-backs now living. † It is, however, only with the pygmy sperm-whales, equally small or even smaller, compared with their gigantic relatives, ‡ that we will now concern ourselves. And we will commence our study with the enquiry as to what are the essential characters of the family to which they belong. Our task is ren

*Teeth are present, however, in the fœtus, but are not functionally developed. † See Cope in Proceedings of the Academy of Natural Sciences of Philadelphia. Beale, a trustworthy observer, has recorded the capture in the "Japan Fishery" of a male cachalot eighty-four feet long; J. D. Bennett has remarked "that the largest size authentically recorded of the sperm-whale is seventy-six feet in length, by thirtyeight in girth; but whalers are well contented to consider sixty feet the average of the largest examples they commonly obtain." Professor Flower, after a critical study, concluded that the length might be about sixty feet, and "ventures to question whether the cachalot frequently, if ever, exceeds that length, when measured in a straight line." The adult Kogiinæ attain a length of from seven to eleven feet.

dered easy by the recent publication of a very elaborate monograph "On the Osteology of the Cachalot or Sperm-whale (Physeter macrocephalus)," by Professor Flower of the Royal College of Surgeons of England, and a full description and illustrations of a pygmy whale, by Professor Owen, who has been the first to clearly elucidate the details of structure of a member of the group of small species.

1. Families of Toothed Cetaceans. There are four families of toothed cetaceans: the Physeterids, or sperm-whales; the Ziphiids, nearly allied to the former, but in some respects approaching nearer to the Delphinids; the Platanistids, containing mostly fresh-water forms; and, finally, the Delphinids, containing by far the largest number of genera and species, and embracing the dolphins (not the fishes of that name), the porpoises, etc. It is on a comparison between the members of all those families that the following characters are shown to be peculiar, either absolutely or in combination, to the Physeterida.

2. Common Character of Sperm-whales. The form is variable, the head being either disproportionately large and blunt in front, with a subterminal blower, as in the giant whales, or conical, as in the dwarfs; the snout, however, always projects forwards, and the mouth is inferior. The cervical vertebræ in whole, or the atlas excepted, are anchylosed together. The hinder ribs lose their heads, and are only connected by their tubercles with the transverse processes of the vertebræ. The costal cartilages which connect the ribs with the sternum retain more or less of their original cartilaginous condition. The skull has the bones raised so as to form a more or less elevated retrorsely convex crest behind the anterior nares. The supraoccipital (so) and parietals combined extend forwards on the sides, and present a convex border projecting forwards high above the temporal fossa, and forwards beyond the vertex. The frontal (f) bones have an extended lateral surface deflected downwards and produced upwards, exposing to view