instances; but very little pollen seems to be carried away by the still appressed lobes of the stigma. When the latter has become somewhat exserted (Fig. 1, s) its lobes expand, and are now ready for fertilization, and as some pollen still remains in the anthers, the flower is now properly hermaphrodite or perfect. The stigma, however, retains its freshness for some time, and meanwhile the remainder of the pollen may have been removed, leaving the flower pistillate in function.

If, now, an insect in search of nectar is attracted to the flower, the purple blotches or nectar marks catch its eye and lead it directly to the mouth of the corolla, its head or back usually com. ing in contact with the receptive face of the stigma if this is already mature. The dense chevaux-de-frise of hairs, however, prevent it from entering unless it be large enough to effect the transportation of pollen in return for the food obtained; but if sufficiently large and strong to pass these, and not too large to creep into the flower, it enters, finding it far easier to follow the guiding groove than to pass over the bristles on either hand. Pushing in a sufficient distance to obtain the desired food, its back rubs against the anthers, or what is equally effective, its sides shaking the filaments, bring down a shower of pollen. Having exhausted the supply of nectar in the first flower, it flies to another, then to a third, carrying pollen from one to the other. Several species of Halictus1 and Calliopsis andreniformis Sm., were seen to visit the flowers in this manner.

If, on the other hand, the insect be too large to force its way into the corolla, it alights on the lower lip, usually clasping the side of the tube with two or more of its feet, and thus steadying itself, while its head is thrust into the flower as far as possible, and its tongue is extended to reach the nectar. Though the modus operandi is different, the result is the same as in the last case, with an exception which will be mentioned later. The flowers are visited in this way by the following insects: Hymenoptera-Apis mellifica L., Bombus virginicus Oliv., B. fervidus Fab., Xylocopa virginica Drury (? and ♂), Megachile brevis Say, M. latimanus Say, Anthidium cognatum Cres., Ammophila vulgaris Cres., Bembex fasciata Fabr., and Myzine 6-cincta Fabr. Lepidoptera-Colias philodice God., Pieris rape L., P. protodice B. and L., Papilio asterias Drury?, Junonia cœnia B. and L., Hesperia hobo1 The Hymenoptera were all kindly identified by Mr. E. T. Cresson.

mok Harris?, H. tessellata ?, Lycana comyntas Harris?, and two species of Nyssoniades. Coleoptera-Chauliognathus pennsylvanicus DeGeer. In addition to these a fly, Mesograpta marginata Say.,1 and one of the species of Halictus mentioned above, were found in considerable numbers collecting pollen from the anthers of young flowers, in doing which they undoubtedly often carry the pollen of one flower to the stigma of another.

Of these insects the species most common in this connection are Apis mellifica, Bombus virginicus and Chauliognathus pennsylvanicus, all of which may be counted by thousands on a bright sunny day about the first of September in places where the plant grows abundantly; and it is upon them, chiefly, that the fertilization of the flowers is dependent. Some of the Lepidoptera, especially Pieris rapæ, are very often seen sipping the nectar of the basil thyme, but from the length of their proboscides they can easily reach the bottom of the corolla without inserting their heads into its throat, and I am inclined to believe that their efficiency in the transfer of pollen is not very great. A noctuid moth, apparently belonging to the genus Prodenia was also very abundant, but in obtaining the nectar it did not rest upon the flower like the species enumerated above, but hovered before it, steadying itself with its fore feet as I have seen Heliothis armigera do when feeding upon the involucral nectar of Gossypium. Though I was somewhat surprised to find a noctuid thus engaged at midday, I find that Harris2 records the habit as not uncommon to certain Agrotids, and it is probably well known to all entomologists.

From what precedes, it may be seen that the nectar of this Calamintha attracts many insects belonging to a considerable number of species, and that the majority of these-in individuals if not in species-readily obtain the sugared fluid, in doing which they encounter the stigma and anthers of the flower-the former (if mature) in entering, the latter before leaving it.

The development of the flowers is such that the self-fertilization of a given flower appears possible in but two ways: 1. Pollen may be taken up by the longer (lower) lobe of the immature stigma as the latter passes below or between the anthers during the elongation of the style, and remaining there, and

1 Identified by Mr. Edward Burgess.

2 Insects Injurious to Vegetation (Flint edition), p. 441.

retaining its virility till the stigma matures, it may then emit its tubes and fecundate the ovules. 2. An insect dusted with the pollen of a flower may revisit the same flower, leaving some of its burden on the stigma; or it may possibly deposit freshly gathered pollen on the stigma as it leaves the flower, but from the position of the stigmatic surface this is not likely to happen. Ordinarily, however, any flower will be fertilized by pollen from another, though from the irregularity with which insects visit the flowers of these straggling plants, this is as likely to belong to the same stock as to a different one.

In closing, it may not be out of place to offer a brief comparison of this species with others of the large family of mints to which it belongs. In this order, nectar is usually secreted— as in the present instance-by a prominent gland that, closely adjoining the ovary, is usually more or less prominently fourlobed, portions of it filling the angles between the lobes of the latter organ. Proterandry, or the maturity of the stamens before the pistil, is the rule, and is sometimes correlated with motions, due to the growth of the parts, by which the anthers and stigma at maturity successively occupy the same place with reference to the other parts of the flower. In some cases strongly marked proterandry, leading to invariable cross-fertilization, has caused the origin of forms with smaller flowers in which the anthers are entirely abortive, so that the species becomes gyno-dioccious. This is the case, for example, with the related Calamintha clinopodium. But a careful examination of the species under discussion did not reveal a similar peculiarity in this case, though further observation, and especially over a more extended territory, may, perhaps, reveal something of the sort. According to Dr. Müller, 1.c., C. clinopodium is visited for its nectar by two lepidopterous insects, Pieris brassica L., and Satyrus hyperanthus L.; and Calamintha acinus is visited for nectar and pollen by the hive bee, and for nectar by a bombyliid fly, Systeochus sulfureus Mik. From the floral structure of the basil, which is quite common in parts of our own country, one would expect its most frequent visitors to be Hymenoptera, and this is supported by what we know of the visitors of C. nepeta; and if so, it is probable that careful examination where numbers of the plants grow in company will reveal the hive bee as among the more frequent.

'Dr. H. Müller, Befruchtung der Blumen, 1873, p. 325.

WHAT

COMPARATIVE NEUROLOGY.

.

BY S. V. CLEVENGER, M.D.

HAT can we say of the nervous system of Protozoa, but that it exists in a diffuse undifferentiated state? If we speak of a nerve force it implies the existence of a nerve, and herein we have the mystery explained. I do not believe in a nerve force after the general acceptation of the term, as a sort of aura residing in and produced by nerve cells. Let us see how much a reconstructed view will account for the hitherto unaccountable. There are certain natural "forces" or vibrations of matter, called sound, heat, light, electricity, etc. Expose albumen to the influence of any or all of them and determinable motions are produced in its mass. Protoplasm has a definite molecular composition which never fails to be susceptible to these influences. The contractile phenomenon is not a whit more of a mystery than the beautiful laws of electrodynamics as deduced by Ampère from the fundamental experiment of Ersted: 1. Two currents which are parallel, and in the same direction, attract one another. II. Two currents parallel but in contrary directions, repel one another. To demonstrate this, one current should be fixed and the other movable. In a few words the Amoeba is the medium for the movable current while its pabulum is equivalent to the fixed current which attracts the animal. I do not mean to lay this down as actually the case, for the causes of Amoebic movements are multiplex, from which, as might be expected, there would be multiplicity of changes in its sarcode. But this alone would indicate how sufficiently the laws of physical forces may some day go to explain the protoplasmic motions.

We see that all matter is mobile. The molecules of the Amoeba are not force proof, and these forces would, from the very homogeneity of the mass, pass in varying directions through the animal as governed by extrinsic causes. But as soon as differentiation began, by even as simple a process as an induration of one part of the protoplasm, currents must be deflected from their former courses. Huxley considers Kleinenberg's fibers of the Hydra as internuncial, and hence the primary form of a nerve. In this case we have a contractile muscle with a nerve differentiated from, and continuous with the muscle. How has this come about?

Immediately upon the definite location of tissue which is more

susceptible to certain external influences, such tissue would quickly differentiate a portion as the path of least resistance, which would also be the most direct conductor of motions from without to the contractile part. Thus the neuro-muscular cells of Hydra appear. From the general mass proceeds the ectoderm, and from it is differentiated the nerve-muscle tissue.

The causes of this differentiation may be conceived by regarding the forms assumed by a layer of the sporules of Lycopodium and sand, when this mixture is subjected to vibrations coarse enough to affect the layer. The electro-dynamic law which draws together matter transmitting currents in one direction would of itself construct a nerve path to contractile tissue.

A nerve, then, is internuncial only, and the ganglion cell is histogenetic. Neither have any force-producing power, but are both the media through which certain molecular vibrations are most swiftly transmitted.

The primitive sense is tactile and all senses have proceeded from its differentiation. For illustrative purposes let us consider energy as divided into molecular vibrations, from one ethereal pulsation in an eternity, to an infinite number of vibrations in one second. In such an undulatory series we may see, as a small division of it, all forces from sound to gravitation represented. While the protozoōn may be visibly affected by every such undulation, the homogeneity of its composition prevents any differential response; for instance, the tremor of a musical note, heat, light, electricity, alike produce contractions or expansions (motions) of its mass. In a higher form of life nerve tissue appears, which conveys only certain vibrations and rejects all others. Take one undulation in a second as the capacity of this nerve fiber. It is a tactile nerve. When a nerve fiber conveys more rapid undulations differentiation begins. Sixteen to forty thousand per second begin and end the auditory vibrations. Quicker vibrations to four hundred and fifty billion per second we may view as heat appreciation, thence to eight hundred billion from red to violet light, above this fluorescent undulations, "chemical energy," electricity, to infinity. We may thus mathematically conceive an

1In a paper read before the American Association for the Advancement of Science, Boston, August 28th, 1880, published in full in the Journal of Nervous and Mental Disease for October, 1880, I treated this subject more with reference to the microscopic anatomy of human nerve systems. Extracts, as above, made from that paper are such portions as refer more directly to our present subject.