VI. CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY No. VI.*- ON THE ANATOMY AND HISTOLOGY OF AULOPHORUS VAGUS.† BY JACOB REIGHARD. Communicated June 11th, 1884, by Alexander Agassiz. MATERIAL AND METHODS. THE material used in the preparation of the following paper was obtained from a ditch by the roadside near Fresh Pond, Cambridge, Mass., in October and November, 1883. In October the surface of the water was so thickly covered by a growth of Lemna as to be almost entirely hidden. Upon gathering the Lemna in a shallow dish, the worms could be easily collected by picking out the tubes which they had constructed from the Lemna leaves. Worms obtained in this way were easily kept all winter in glass jars containing water, in which some additional Lemna had also been placed. They lived and multiplied rapidly, even when not exposed to the sunlight. For sectioning, the specimens were prepared by the use of either Kleinenberg's picro-sulphuric fluid, osmic acid, or chromic acid, good results being obtained with each. Borax-carmine, or a mixture of borax-carmine and picro-carmine as recommended by Bülow for Lumbriculus, was found to be the best staining fluid. The worms curl in a dorso-ventral plane in the killing fluid, but they may be straightened by placing them on a glass slide between the edges of two square cover-glasses, which are closely applied to the slide and held in position by wetting their under surfaces. The straightening is accomplished by sliding the cover-glasses against the worm, one on each side, care *No. V. of these Contributions appeared in the Quart. Jour. Micr. Science, Vol. XXIV., N. S., 1884, under the title, "The Development of Phryganids, etc., by WILLIAM PATTEN." † Prepared under the supervision of Dr. E. L. Mark. being taken not to crush it. This may be done by arranging two pieces of wire, of the diameter of the worm, so that their ends project between the edges of the cover-glasses. The glass slide may be laid for the purpose on a piece of wood, into which the other ends of the wires are fastened. After being straightened in this way, they may be rendered rigid enough for handling by placing on them while still between the cover-glasses a few drops of 70 per cent alcohol, in which they should remain for a minute or two. They are most readily handled by means of a pipette. GENERAL DESCRIPTION AND HABITS. Aulophorus vagus was named and described by Leidy in the American Naturalist for June, 1880, as follows:-"Our species I propose to name Aulophorus vagus. Body cylindrical, compressed, transparent, with red blood and yellowish-brown intestine. Single individuals of the third of an inch or more in length, composed of from 24 to 35 rings. Head ovoid, extending as a conical upper lip, very mobile and changeable in form, obtuse or sub-acute and minutely hirsute. Eyeless. Caudal ring contracted, and furnished with a pair of long, divergent, digit-like appendages, which are straight or slightly incurved, blunt, and minutely hirsute. Anal aperture surrounded by a rosette of half a dozen prominent, blunt, conical papillæ. The four rings succeeding the head furnished on each side with fascicles of seven to nine podal stylets; the succeeding rings, except the last, with fascicles of 5 to 6 podal stylets, which are shorter than the former. Podal stylets sigmoid with a median shoulder and ending in a furcate hook. The same posterior rings furnished dorso-laterally with fascicles consisting each of usually a single moderately long bristle and a single nearly straight stylet ending in a spade-like expansion. Pharynx capacious, going into the fifth ring, and narrowing into an œsophagus, which ends in the intestine within the ninth ring. Generative organs unobserved. Worm of 3 to 5 lines in length, or more, according to its degree of extension. Living in a tube of its own construction, which it drags about with it. The tube is composed of a transparent cement or basis, incorporated with various materials, such as vegetal particles, sand, dirt, diatoms, spongilla spicules, etc. In creeping about among aquatic plants, Lemna and Wolffia, the worm stretches in such a manner that one third of the body extends from the fore part of the tube, while the forked caudal extremity remains projected from the back end. The worm moves in jerks, alternately extending the fore part of the body and projecting the podal fascicles forward and hooking into the surface on which it is creeping, and then contracting the fore part of the body and dragging along the back part enclosed within the tube. Frequently the motion is aided by eversion of the pharynx, so as to form a disc or sucker which adheres to surfaces like that of a leech. The movements occur in quick succession, so that the worm creeps about quite actively. At times it doubles itself, thus passing through its tube and reversing its direction. At times, too, it will leave its tube and creep about without one. The papillæ of the anal aperture are clothed with vibratile cils, which produce an active current inwardly as observed in Dero." The animals are found either single, or composed of 2 to 4 zoöids joined by bud-zones. In March, material kept over winter showed few specimens with bud-zones, and in the great majority of cases the number of segments was 25. The body tapers slightly posteriorly. It ends in an expanded pavilion resembling that described by Perrier for Dero obtusa. This pavilion (Pl. I. fig. 1, pav.) opens somewhat dorsally, and, when fully expanded, shows no trace of lobes on its dorsal and lateral borders. On its ventral border it presents in all cases two lobes, which are separated by a median notch and project slightly beyond the rest of the border of the pavilion. When the latter contracts, the dorsal and lateral borders become divided into four addi tional lobes by a median dorsal and two lateral notches. Thus, unless it is examined when fully expanded, the pavilion presents the appearance of "half a dozen prominent, blunt, conical papilla" surrounding the anus, as described by Leidy. When the animal is in plenty of water, the posterior part of the body is habitually kept bent upward, so that the opening of the pavilion is toward the surface of the water. The digit-like appendages are attached laterally and ventrally, outside the border of the pavilion. Their outer ends are slightly swollen. They project directly backward parallel to one another when the pavilion is contracted; when it is expanded, they diverge. The number of podal stylets in each of the fascicles of the four anterior ventral pairs varies from 8 to 14, but they do not differ from one another at all, except in length, and this, taken in connection with the fact that they are fewer and more uniform in size in immature zoöids, gives no support to the notion advanced by Perrier (72, p. 68) for Dero obtusa, that the fascicles are formed by the fusion of ventral and dorsal fascicles. The stylets in the ventral fascicles differ from those in the dorsal, and one would hardly expect this difference to be obliterated by a fusion of the two. The stylets in these four anterior pairs of ventral fascicles (Pl. I. fig. 2) are longer and straighter than those in the succeeding ventral pairs. The fork on the convex side of the furcate outer end is much longer, sharper, more curved, and more slender than that on the concave side. The number of stylets in the ventral fascicles behind the fourth pair varies from 4 to 7, perhaps according to the age of the animal. They also vary in length. The fork on the convex side of the stylet (Pl. I. fig. 3) is very much smaller and sharper than that on the concave side, but not so long. These stylets are therefore readily distinguished from those in the first four pairs of ventral fascicles. The dorsal fascicles contain from 1 to 3 bristles, and from 1 to 3 spade-shaped stylets. The latter (Pl. I. fig. 4) are not so much curved as the ventral stylets. Their outer ends are flattened and expanded into thin triangular blades, one edge of the expanded portion being nearly straight, and the other concave, and both being strengthened by marginal ribs. A third rib sometimes runs midway between the two marginal ones. The bristles are much longer than the stylets, pointed, and without a median shoulder. The matrix cells of the stylets and bristles may be seen in sections. They have elliptical, granular nuclei, which are closely applied to the stylets and bristles. In the fall, when the Lemna leaves were plenty, the tubes were formed entirely from them. Specimens kept over winter in glass jars in which there was but little Lemna formed their tubes entirely from Plumatella eggs, as described by Leidy. An isolated specimen in a small dish with some Edogonium formed its tube entirely from the Edogonium filaments. The worms were never observed to leave the tube voluntarily, nor were any ever found without a tube. When a single individual becomes divided into two, the two sometimes continue to occupy the same tube, one reversing its direction; or the newly-formed individual may build a new tube by the side of the old one and attached to it. An individual removed from its tube forms a new one in a very short time, frequently in less than ten minutes. The animal is easily driven from its tube by following it up from the posterior end with needles. They stay most of the time at the surface of the water, and, when in a dish, usually at the side. There they lengthen their bodies, head downward, and seize the side of the dish by using the everted pharynx as a sucker. Then, by alternately shortening and lengthening the body, they continually move the tube up and down. The alimentary canal of the worms found at the surface of the water frequently contains a great many large air-bubbles, but such bubbles have never been seen in animals taken from the bottom of the jar. The bubbles are especially noticeable in specimens whose tubes are formed of heavy material, and not of Lemna leaves nor Plumatella eggs. It would seem, then, that when its tube is heavy the animal has the habit of swallowing air-bubbles to keep it afloat. When driven from its tube, it swims about like a water-snake, but immediately seeks cover. Its food consists of diatoms and other unicellular Algæ and small water animals of every kind. The only method of reproduction that I have observed is that by budding. No attempt has been made to determine the existence of a numerical law governing the budding process. The phenomena do not seem to differ from those described for related forms. In the sixth and seventh segments rounded cell-masses have been seen, which are probably the rudiments of the testes and ovaries, but they were never sufficiently developed to allow a satisfactory study of them. ANATOMY. The Body Wall. The body wall consists of four layers, in the following order, from without inward: a cuticula, the matrix of the cuticula or dermis, an annular muscular layer, and a longitudinal muscular layer. The cuticula is a thin structureless membrane covering the entire surface of the body. It is easily seen in all sections, and may be demonstrated by leaving the animal for half an hour in a very weak chromic acid solution, or by using a very weak solution of potassium hydrate. Frequently, when the animal dies in water, the cuticula becomes raised up into vesicular swellings and is thus rendered plainly visible; when some part of the animal, as a digitiform appendage, is crushed, it then also shows plainly. The cuticula presents no markings under a power of six hundred diameters. The matrix of the cuticula, the dermis, consists in most regions of a single layer of prismatic cells. The latter are, however, several layers deep on the frontal lobe. This layer is thicker at the head and tail ends, and in the region of the head and tail it is also thicker on the ventral than on the dorsal side. The dermal cells have large granular nuclei, the walls of which are frequently more distinct than those of the cells themselves. Each nucleus contains one or several nucleoli. The cells and their nuclei are longer in the head and tail regions than elsewhere. Many unicellular dermal glands (Pl. II. figs. 11, 13, drm. gl.) are found in the region of the head, especially on the frontal lobe, and a few in the region of the pavilion. These glands vary in shape. Frequently |