The likeness between the chain of ganglia in the leech and the spinal cord of Vertebrata has led many comparative anatomists astray in homologizing. A nearly similar chain of ganglia obtains in Vertebrata but situated ventrally from the vertebral column. This chain is a first system. The head ganglion, only, of the leech, as in most Invertebrata can be compared to a spinal. In Insecta and Myriapoda the superimposed secondary becomes more evident. An "unpaired system" runs in the median line between and connected with the paired or primary system, typifying the more definite appearance of the medullary gray and its commissures below or back of the head.

Todd and Bowman (pages 611 and 614, Vol. 111) use the following words, which indicate an early recognition of the anatomical fact without their having seen its connection or full import: "In the bee the cerebral ('secondary') ganglion is very large; from its anterior portion is given off two nerves which pass forward to the base of the antennæ and have their origin well marked by a distinct ganglionic enlargement !"

Todd dwells upon the importance of recognizing this distinct ganglionary enlargement, and repeats, "The sensory nerves have ganglionic enlargements in the bee."

(This appearance of a third system is rare in Invertebrata, though the crab and Pterotrachea also may prove to be its possessors.)

The ganglionic swellings which on the sensory nerves of the bee distinguished it from most Invertebrata, in vertebrate types from Cyclostomes upward become more markedly developed.

While both the first and second systems possess recognized afferent and efferent fibers, before being able to comprehend the relationships between systems or the process of projection formation, we must consider whether some fundamental law does not underlie these series of relations which will better account for their creation.

The typical segment is an animal whose nerve center lies midway between an afferent and efferent strand, thus: ☀. A series of such segments, if ununited, present this appearance:

These segments could be correlated by a second fiber, which

instead of passing between peripheries as in the instance of nonunion, unite the segmental ganglia by making another ganglion its motor projection.

Carpenter ("Principles of Comparative Physiology," p. 642) expresses this view: "When different organs are so far specialized as to be confined to distinct portions of the system, and each part consequently becomes possessed of a different structure and is appropriated to a separate function, this repetition of parts in the nervous system no longer exists; its individual portions assume special and distinct offices, and they are brought into much closer relationship to one another by means of commissures or connecting fibers, which form a large part of the nervous system of the higher animals. It is evident that between the most simple and the most complex forms of this system there must be a number of intermediate gradations, each of them having a relation with the general form of the body, its structure and economy, and the specialization of its distinct functions. This will be found, on careful examination, to be the case; and yet, with the diversity of its parts as great as exists in the conformation of other organs, its essential character will be found to be the same throughout."

Segmental union, thus, is accomplished through efferent nerves no longer penetrating to primary organs, but passing to nerve centers of other segments, for the purpose of producing coördinated movements, and consequently to exert an inhibitory effect thereupon.

[To be continued.]

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BOTANIZING ON THE COLORADO DESERT.

BETWEEN

BY EDWARD LEE GREENE.

II.

ETWEEN Coyote Wells and the next station lie some twentytwo miles of almost uninterrupted plain. The white clay soil, strong with salts and alkalies, produces no cacti, but there is great abundance of chenopodiaceous shrubs, popularly called grease wood. Yet there is no verdure even here; for although the grease bushes, contrary to the rule of desert growths, are leafy, their abundant foliage is of precisely the same dull whitish color as the clay in which they grow. Over this smooth and slightly yielding clay the walking was very easy, and I made

good time, for as the objects of interest on this particular day's march did not promise to be numerous, I intended to shorten as much as possible the hours of inevitable suffering from thirst.

During the first half of the day a mirage, like a narrow sheet of placid water, just far enough away to dazzle and pain one's eyes, kept always its allotted distance ahead. By the wayside and over all the plain, were scattered the shells of a certain fresh water mollusk of the genus Unio. The nearest stream is the Rio Colorado, full a hundred miles distant, and these shells, now more than half dissolved and crumbling into scaly purple fragments when you touch them, must have been deposited here at a time when the Colorado had flooded the whole desert. No flower or bird or insect were seen to-day to vary the monotony or break the silence. At noon I detected the shape of an adobe hut upon the tremulous horizon away to the left of the stage road, probably a mere ruin, but nevertheless suggestive of water, since no one ever built an adobe wall in this wilderness without first having found water. The first impulse was to turn aside and visit the spot. But as, through the varying medium of the heated air, the adobe at one moment seemed near, and the next very far off, so that I could not guess whether it was one mile away or five, I at second thought resolved not to waste time in what might prove a long and worse than fruitless deviation from my proper course. Before the afternoon was half gone my twenty-two miles journey was ended. I had reached the station of Indian Wells. The third day's travel witnessed another change in the character of the soil. The ground becomes sandy, and instead of the grease wood of the alkali flats we have the much more sightly creasote bush (Larrea mexicana Morie), a bright evergreen with small foliage somewhat resembling that of the dwarf box, though the shrub has nothing of the close, compact habit of the box, and its slender spreading or rather drooping boughs bear yellow blossoms among the leaves.

The twigs when bruised exhale a strong odor of creasote, and they have stimulating properties. The Indians and Mexicans journeying across these parched wastes, chew them, and even tie bunches of them to the bits in the mouths of their ponies with good results in cases of extreme suffering from fatigue or thirst. This shrub occupies the sandiest parts of the desert, and usually where it occurs no other species of vegetation is found.

After some eight or ten miles of sand came another change of soil, and the creasote bushes gave place to the mezquit, a small tree of considerable importance in the Southwest. This was the first mezquit wood I had ever seen; I therefore turned aside from the road to walk among the trees, wishing to inspect somewhat carefully the characteristics of the species. Very suddenly my attention was called to certain objects interesting in quite a different way. The noonday silence was broken by a shout, and turning toward the quarter whence the voices had seemed to emanate, I discovered a dozen naked savages, some standing, others sitting under a mezquit tree. After a little experience of travel in Western wilds, one learns not to be always afraid of Indians; yet I confess on this particular occasion a full inventory of the traveler's feelings might have shown some fears. I was alone, unarmed, and at a rather unsafe distance from any habitation of civilized men. If the barbarians should, for any purpose, see fit to make away with the defenceless saunterer, and put his bones to rest beneath the sands, they could do so with perfect safety to themselves. They were stalwart fellows, quite different in appearance from the members of any Western tribe with which I was familiar; moreover they had displayed unusual boldness in their yelling out and commanding me, as they did by word and gesture, to leave my own course and come and pay to them my respects. But whoever upon finding himself in the power of savages feels any timidity had best conceal it. I, therefore, with an air of calmness and confidence marched forward and seated myself in the sand in the midst of the swarthy group. For a while no one spoke. Indeed, their knowledge of the learned languages was presumably not much more extensive than mine of the dialect of the Yumas. But the Yumas have inquisitive eyes, and they studied their visitor in silence. Presently the oldest looking one among them discovered something which evidently interested him. It was a plain heavy ring, rather specially valuable to me as having been made from a nugget of Australian gold which a friend from that far off southern coast had given me. The Indian pointed to this and asked if it was "oro." Feigning a confidence which I was far from feeling, but judging it the wisest thing to do under the circumstances, I slipped the ring from my finger and passed it over to him. He placed it upon the 1 Spanish for gold.

palm of his hand and gave it a slight toss in the air, thus testing to his own satisfaction its weight and genuineness. Each one of the speechless company went through the same performance, and then the ring was handed back to me by the one who had first received it, greatly to the quieting of my nerves. And now my botanist's portfolio had to be examined. It was well filled with flowers, and boughs and twigs of desert bushes, with which my interviewers were familiar. They all gathered close about me to admire my herbs, and then entered into conversation among themselves, discussing, I dare say, the question of my object in gathering up these things. They gave me their names for certain of the plants and then inquired what I called them. Presently he who seemed the chief man among them expressed to me his opinion that I was a "medico," and I felt that I was safe. Composedly I now surveyed the persons of these representatives of a tribe that was new to me. In appearance they were the least repulsive of all the Indians I had ever seen. Every one of the party must have measured at least six feet in height; and clad only in their breech clothes, each displayed a development of form and figure well nigh faultless. Their faces, too, really bore an expression of mildness and good humor not commonly noticeable in aboriginal Americans. In short, I beheld for the first time a group of rather handsome Indians. What their business may have been here in the midst of the desert, so far from their homes on the fertile banks of the Colorado, I cannot guess.

To-day the distance from station to station was thirty-two miles. Happily for the pedestrian there is a well mid-way between the stations. This place of refreshing was arrived at within a half hour after I had concluded my visit at the encampment of Yumas. It is called New River Well; not because there is any river there or ever was. There is, however, a broad and shallow channel where once, since white men began to traverse the region, there flowed for a few hours a broad and turbid stream. Though the flood was transient, and no one could tell whence it came, the fact sufficed to give the place the name of New River. A deep well has been sunk at this point by the stage company. The water, though clear and cold, has such a sweet, nauseating and rather metallic taste that no one drinks of it unless impelled by most inordinate thirst; however, it does not seem to be at all unwholesome. There is no describing the almost maddening thirst which