We made a large number of dredgings but the dredge used was too coarse and heavy for such work, and as we had had no idea of finding Amphioxus at this place, we were unprovided with one of suitable construction. It is probable that with a proper dredge, perhaps a ring dredge, made light and with fine meshes, they could be taken in this locality in fair numbers, and it is possible that places might be found along our coast, if searched for, where they could be taken in as great abundance as at Naples and Messina, in Italy. And where the adults are found the young could be taken also, if looked for during the breeding season, which in this country is probably during the months of June and July. I base this statement upon the facts that my young specimens, which were somewhat advanced in development, were taken mostly during the second and third weeks of July, and that only one specimen could be secured after the close of that month. Amphioxus does not appear to be a difficult animal to keep if supplied with plenty of sand in which to burrow, and a daily change of water of a density equal to that which is found at the place of its capture, My adults remained alive and appeared to be in fine condition as long as I could give them water which came in fresh from the sea every day, but in September they were carried up the bay to Tangier's sound, where being unable to supply them with suitable water they soon showed unmistakable signs of debility, and on the 10th inst. they were placed in picric acid to be ready for future service. None of the young remained alive as long as did the adults, and only a few grew so well and appeared so vigorous as to indicate that they would reach maturity. Some of them, from some cause, became dwarfed and drawn out of shape so as to look, in one or two cases, like a large letter S, and others, probably from the erosive or wearing action of bits of sand, or something of the kind, which had entered the stomach and intestines along with the food, had lost portions, and sometimes half of their bodies, and yet these little deformed and maimed animals lived sometimes for a week in such condition, evincing certainly a good degree of vitality, and enabling us, if Amphioxus is really one of the earliest of animals, the better to appreciate the "why and the wherefore" of the persistence of this species to present time.

The Skeleton.-The framework of Amphioxus is entirely cartilaginous, and is composed of the notochord; a series of processes

said to represent spinous processes, which extend along nearly the entire length of the dorsum, and along the ventral side of the tail portion of the animal; and a series of arches or supports which are formed along and in the sides of the anterior half of the alimentary canal. The notochord has already been described, and its position defined as forming an axial support extending from end to end of the body, and representing the back bone of higher vertebrates, but lacking the anterior expansion or brain case. The spinous processes form rows of semi-transparent, perpendicularly placed, block-like bodies; the dorsal row originating over the chorda dorsalis, and rising upwards from between the side muscles to form a median basal support to the dorsal fin; and the ventral row originating beneath the intestine and extending out from between the side-muscles to form a support to that portion of the median fin which extends from the branchiopore back to the ventral "blade" of the tail. These blocks are well marked, and form quite a prominent border to the greater part of the outline of the muscular portion of the body. (Figs. I and 5, Pl. 1, and Fig. 7, Pl. 11.) The series of bodies pertaining to the alimentary canal consist of a mouth ring, a pharyngeal ring and a variable number of rib-like arches placed alternately upon either side of the canal and extending back to about the middle of the body. These different parts are unconnected above, unless it may be to a slight extent with the sheath of the notochord, but below, the two rings, which arise from a common base, are connected with the arches by a cartilaginous trough-like formation which extends back as far as the last arch, and in the sides of which the bases of the arches are firmly imbedded. The mouth ring is formed in the integument of the edges of the mouth orifice, and arches forward and upward in conformity to the outline of this portion of the body. It is made up of segments, one for each tentacle, and each segment sends out from the side, at the anterior end, a long, slender prolongation which extends, as a central support, to the very tip of its corresponding tentacle. (Fig. 2, Pl. 1.) These segments, which are the same in number upon both sides of the mouth, do not unite in front, but form arms which end upon either side just at the base of the ramlike extremity of the body, and at these terminations of the "ring" new segments are formed, when, in the growth of the animal, there is room in the oral circlet for additional tentacles.

The odd tentacle which is found in the mouth circlet of Amphioxus, is formed from the center of the basal portion of cartilage from which the two rings originate. The cartilaginous portions of all these tentacles are curved inward, and so directed that the tentacles in the normal condition always cross each. other, much as the fingers of a person's hands can be interlaced, and thus form a rude sieve which prevents the entrance of large substances into the digestive tract. The pharyngeal ring which marks off the anterior limits of the abdominal cavity, forms a sort of welt or slight constriction around the inside of the anterior portion of the alimentary canal. It is curved backwards upon both sides, and bears upon the posterior border of each curved portion two or three rather large fleshy-looking tentacles. (Fig. 2, Pl. 1.) These tentacles generally lie directed backwards against the side walls of the digestive tract, but they can be brought forward so as to extend directly across the canal and form a second barrier to the onward progress of large bodies. In the young this barrier is of much greater service in preventing entrance to the digestive tract than the oral tentacles, as these latter appendages are not sufficiently numerous to act as an efficient guard until the animal is of considerable size, as large or larger than the largest of my young specimens. These tentacles are not always of the same size, and are generally so placed upon the sides that when brought forward they alternate one above the other.

The branchial arches are frame-like in structure, long and slender in outline, and run obliquely downwards and backwards across the entire width of the canal-this obliquity is such that the center of the upper portion of one arch is about over the center of the lower part of the next arch in front. The arches are quite numerous, fifty, more or less, upon each side, but I am not aware that there is any definite limit to their number, the largest individual appearing to have the most arches. The greater number of them are of uniform length, but as they approach their posterior limits they gradually become shorter and shorter, to the last one or two, which are less than a quarter the length of the longest ones. The first and second arches are also much shorter than the others, and are about the length of the last ones. The first and last arches are very simple in formation. The first is composed of an oblong framework, pointed at the lower end and nearly square or somewhat pointed at the upper. It is about

twice as long as broad, almost upright in position, and is placed just posterior to the lower curvature of the pharyngeal ring. The last one is merely a round or nearly round ring of cartilage. The rest of the arches are shaped much like the first, but are bi-lobed above and have a central bar which passes from the indentation of the bi-lobed end down to the cartilaginous bed which encloses the pointed lower extremity. This bar is about twice as wide as either side of the arch, and is marked throughout its entire length by a median line which indicates a division into two slender halves. In all of the longer arches there are also three crossbars, which pass from side to side of the arch at about equal distances between the two ends, and in the shorter arches, exceptthe first and last, which contain none, there are sometimes one, sometimes two of these bars in each arch. These bars pass obliquely backwards and upwards across the arch, and generally go directly from one side to the other, but some of them divide at the central bar and become attached to it, so that they form two short bars instead of one long one. The arches of each side are placed close together, edge to edge, so that they have the appearance of a connected, continuous series of long slender oblique bars, each marked by a median division line and separated by a space of about the same width as the bars themselves, and with cross-bars running, with more or less regularity, across these spaces from alternate bars. The upper edge presents a series of uniform lobes, and the lower edge a series of larger uniform arched points, there being left between each two points a triangular space of considerable size. (Fig. 4, Pl. 1, a.) Each complete arch is thus made up of two nearly similar halves, and as the arches of the two sides alternate with each other, as has already been said, the triangular spaces at the bases of the arches not only serve to show the divisions between them, but also indicate the positions of the opposite arches. This alternation can. be readily seen by placing an adult animal, when living, under a low power of the microscope, or by a careful dissection of this portion of the body.

The Digestive Tract.-The alimentary canal, which extends along beneath nearly the entire length of the notochord, is somewhat compressed from side to side, varies considerably in breadth in different parts, and is lined throught its entire length with cilia which serve by their action to draw food into the canal for the

nourishment of the animal. The canal may be divided into five rather natural divisions; the mouth cavity, extending from the mouth orifice to the pharyngeal ring; the pharynx, the œsophagus and the stomach, extending from the pharyngeal ring to the division between the abdomen and tail, and which hang from their attachirent beneath the notochord freely suspended in the abdominal cavity, being completely enclosed by its walls; and the intestine, which extends along through the tail portion of the animal to the anus, near the posterior extremity. The mouth cavity, or first division of the canal, is somewhat triangular in shape, being circumscribed above by the notochord, and below and behind by the two orifices already mentioned. Its anterior upper outline is curved, and it bears upon its walls certain slight, finger-like ridges where the cilia of this cavity are principally aggregated.

At the rather constricted opening of the pharyngeal ring it merges into the pharynx, which extends a little past the middle of the abdominal cavity, and is the largest division of the canal. This portion is that in which the branchial arches are formed, and has much the shape of a bean pod, being quite broad along the central part and narrower towards each end, but the posterior extremity tapers much more gradually than the anterior, and where it merges into the cesophagus, it is hardly more than half the size of the portion at the pharyngeal ring. Along its sides, in all the spaces between the bars of the branchial arches, there are long narrow openings, called branchial slits, which place the interior of the pharynx in communication with the abdominal cavity, which is also known as the branchial cavity, or atrium, but which might more properly, perhaps, as will be noted later on, be called the branchium. These branchial slits extend, with few exceptions, from the upper curves down through nearly the entire length of the arches, to the edges of the cartilaginous, troughlike bed, being crossed here and there by the cross-bars which serve to stiffen the general framework. In the first two or three arches the clefts do not extend quite to the upper borders. Along the inner edges of these slits the cilia of the pharynx are very long and arranged in rows completely encircling each slit (Fig. 4, Pl. 1), so that by their action they intercept the food particles which are brought into the canal and which might pass through the slits and drive them onward towards the stomach, but allow