The differences are really great (when compared to the differences between genera of the same family at a similar time of life) in all lepidopterous larvae, as well as in all Orthoptera which have come under my notice. No attempt to coördinate these differences, or to study their meanings, or to show the nature of their evident relationship to hypermetamorphosis, has ever been made.

Not less inviting is the boundless region of investigation into the habits of insects and their relation to their environment. The impulse given to these studies by the rise of Darwinism, and the sudden and curious importance they have assumed in later investigations into the origin and kinship of insects, need only to be mentioned to be acknowledged at once by all of you. The variation in color and form exhibited by the same insect at different seasons or in different stations, "sports," the phenomena of dimorphism, and that world of differences between the sexes, bearing no direct relation to sexuality; mimicry also, phosphorescence and its relations to life, the odors of insects, the relation of anthophilous insects to the colors and fructification of flowers, the modes of communication between members of communities, the range and action of the senses, language, commensalism,-these are simply a few topics selected quite at random from hundreds which might be suggested, in each of which new observations and comparative studies are urgently demanded.

The fundamental principles of the morphology of insects were laid down by Savigny in some memorable memoirs more than sixty years ago; the contributions of no single author since that time have added so much to our knowledge, notwithstanding the aid that embryology has been able to bring. Nevertheless there remain many unsolved problems in insect morphology which by their nature are little likely to receive help from this source. Let me mention three:

The first concerns the structure of the organs of flight. The very nomenclature of the veins shows the disgraceful condition of our philosophy of these parts: the same terminology is not employed in any two of the larger sub-orders of insects; names without number have been proposed, rarely however by any author with a view to their applicability to any group outside that which

1 Notice Meyer's beautiful studies on the perception of sound by the mosquito.

formed his special study; and a tabular view which should illustrate them all would be a curious sight. A careful study of the main and subordinate veins, their relations to each other, to the different regions of the wing, to the supporting parts of the thorax and to the alar muscles, should be carried through the entire order of insects; by no means, either, neglecting their development in time, and possibly deriving some assistance in working out homologies by the study of their hypodermic development.

The second concerns the mouth parts. The general homologies of these organs were clearly and accurately enough stated by Savigny, though one may perhaps have a right to consider the last word not yet said when one recalls Saussure's recent claim to have found in Hemimerus a second labium. What I refer to, however, is another point: it relates to the appendages of the maxillae and the labium. Considering the labium as a soldered pair of secondary maxillae, we have at the most, on each pair of maxillae, three appendages upon either side. These appendages, as you know, are very variously developed in different sub-orders of insects, or even in the same sub-order; and it has at least not been shown, and I question if it can be done, that the parts bearing similar names in different sub-orders are always homologous Here is a study as broad and perhaps as difficult as the

organs. last.

The third is the morphological significance of monstrosities, especially of such as are termed monstrosities by excess. The literature of the subject is very scattered, and the material much. more extensive than many of you may think. At present this subject is, so to speak, only one of the curiosities of entomology, but we may be confident that it will one day show important relations to the story of life.

After all the labors of Herold, Treviranus, Lyonet, Dufour, and dozens of other such industrious and illustrious workers, some of you would perhaps ask: Is there anything important remaining to be done in the gross anatomy of insects? Let the recent work of some of our own number answer, which has shown in the Hemiptera and Lepidoptera the existence of a curious pumping arrangement by which nutritious fluids are forced into the stomach. It is certainly strange that after all that has been said as to the mode in which a butterfly feeds, that no one should have dissected a

specimen with sufficient care to have seen the pharyngeal sac which Mr. Burgess will soon show us. No! the field is still an open one, as the annual reviews clearly show. The curious results of Flögel's studies of the brain, the oddly constructed senseorgans found by Graber and Meyer (early noticed briefly by Leydig) in the antennae of Diptera, the important anatomical distinctions discovered by Forel in different groups of ants, the strange modification of the tip of the spiral tongue in Ophideres, which Darwin, Breitenbach and Künckel have discussed, and, above all, the extensive investigations of the nervous system in insects, generally, which Brandt has recently undertaken, and the keen researches of Graber in various departments of insect anatomy, show, by what has been accomplished, how many harvests are still unreaped. The microtome, too, has put a new instrument of precision into the hands of the investigator in this field.

We might in the same way point out some of the special needs in the study of the finer anatomy or histology of insects, but the pressure of other duties forbids a further pursuit of the subject. Enough surely has been suggested, even in this hasty sketch, to show that we cannot yet rest upon our oars, but must push forward undaunted into still unknown waters. If these few words shall arouse in any one a higher ambition leading to better work, their aim will have been accomplished.

PAPERS READ.

FURTHER NOTES ON THE POLLINATION OF YUCCA AND ON PRONUBA AND PRODOXUS. By C. V. RILEY, of Washington, D. C.

Ar the Dubuque meeting of the Association, in 1872, it was my privilege to lay before you the substance of a then unpublished communication to the Academy of Science of St. Louis, embodying sundry facts regarding an interesting and anomalous little. moth (Pronuba yuccasella, fig. 1), and its connection with the pollination of our Yuccas. The observations were made in the year 1872 and are recorded, with additional facts ascertained in 1873, in the Transactions of the above-named Academy (Vol. III, pp. 55-64 and 178-180), the American Naturalist (Vol. VII, Oct. 1873) and my 5th and 6th Reports on the Insects of Missouri. As the facts have never been published in our Proceedings, I will present the more important of them by brief recapitulation.

The moth (fig. 2,b,c,) has an immaculate white upper surface, and fuscous under surface in both sexes, and rests during the day for the most part within the half-closed flowers, the protective coloring of which serves to conceal it. The male possesses no very marked characters, but the female is most anomalous; first, in possessing a pair of prehensile, spinous, maxillary tentacles (fig. 1, b) found, so far as we now know, in no other genus of Lepidoptera; second, in possessing a long, horny ovipositor (fig. 1,j, and fig. 3), adapted to piercing and penetrating — a structure equally exceptional among Lepidoptera: "When the ovipositor is entirely withdrawn, the tip of the abdomen [fig. 3, a] presents a truncate appearance, the terminal joint being bluntly rounded at tip, with a slight projection both above and below, and a corrugated ridge dorsally a little in advance of the tip. This terminal joint is very much compressed from the sides, with a few stiff hairs around the terminal borders. The ovipositor issues from the middle of the truncate end, is very fine, tubular, the basal