In the spring of 1869, while at work on the study of a question. connected with the common eel, Anguilla acutirostris,* my attention was drawn to a small white speck embedded in a morsel of fat on the intestine of that animal. As said above, its color was white, while the fat of the fish is quite dark. It was this contrast that made it so easily observable, although it was of very minute size; for in its greatest length it was not much more than the onetwentieth of an inch; and its breadth at the forward end, which

*This name, Anguilla acutirostris, is one of the twenty and odd synonymes given to the common eel of Europe, first systematically referred to the genus under the name of A. vulgaris. Dr. Günther refers a specimen received from New Jersey and in the Liverpool Museum, to the same species as the European, but considers our common eel, which also has been described under many names, though best known under that of A. Bostoniensis, as distinct from A. vulgaris of Europe, although identical with specimens from China and Japan.

From extensive comparisons of specimens collected by the hundreds from the salt and fresh waters of Massachusetts, and from Lakes Champlain and Erie, with several from England and China, I have little hesitation in referring our A. Bostoniensis with all its marine and fluviatile uncles and aunts, grandfathers and grandmothers, back to its super great grandparents; to one and the same species with the common eel of Europe, uniting them all under the name of Anguilla vulgaris, or the Muræna Anguilla of Linnæus and the old writers. Either this must be done or almost every hundredth specimen collected must be regarded as the type of a distinct species, for a perfect series from long heads to short heads and long tails to short tails, thick lips to thin lips silvery color to black, etc., etc., can be made out of any large lot, and no set of character, can be selected as of specific value without finding them worthless for the purpose in almost the very next specimen taken in hand.-F. W. PUTNAM.

Entered according to the Act of Congress, in the year 1872, by the PEABODY ACADEMY OF SCIENCE, in the Office of the Librarian of Congress, at Washington.

AMER. NATURALIST, VOL. VI.

29

(449)

Fig. 117.

was the thickest part, was about one-eighth of the entire length. That it was an individual organism I had not the least suspicion. It was solely its white color, in such direct contrast with the dark adipose tissue, in which it was contained, that excited my curiosity. On this account it occurred to me that the microscope might reveal some difference in structure. Having put it under a lens of very moderate power, I was surprised to see a vermicular object, with the thick end truncated. Now a deep regret seized me; for I supposed that in the dissection of the eel, the most important part of this interesting specimen had been unwittingly cut off. The appearance thus presented in the microscope is shown in Fig. 120, where it looks like a worm with its anterior end excised. Thus regarding the object as ruined by an untoward accident, I was about to cast it aside, when lo! to my glad astonishment, the creature began a singular movement at the supposed decapitated end. Astonishment is not the word-it was in amazement that I gazed upon that strange movement. Such a sight could never be forgotten. Who does not remember the childlike delight at seeing for the first time a juggler draw the almost interminable cornucopia out of his mouth, until the mountebank's head looked like that of the fabled Unicorn? But that was only a smooth paper cone, after all; and the trick of it every schoolboy well understands. Not so with this feat of my puny capitve; at whom I had the lone privilege of gazing through this wonder-peering instrument. Like the sheriff, who was obliged on account of his pleasant bearing, to respect the unwelcome tenant whom he had just ejected; so I must confess that this unpleasant occupant whom I had ousted from its strange dwelling-place, had compelled my admiration, by a singular gracefulness of form and

Fig. 118.
a

Longitudinal section of E. gigas, showing proboscis re

tracted, the hooklets still exterprotractile muscles. cc, the re

nal. a, the oral pore. bb, the

tractile muscles. (From Owen.)

movement, albeit certain outré and weird-like accomplishments. With a slow, steady and uniform movement, a beautiful and tiny structure rises up, until the truncated end is capped or surmounted by a pretty little pagoda, with many circlets of hooks, the distance from ring to ring, being uniform. It was as

The

if a miniature tower had risen out of a little
crater, and covered it with its base.
whole structure is pellucid, like old milky-
white china. So that now the end that seemed
to be cut across is completed by having a cone
projected on it as a base, the apex terminating
almost in a point. At this extremity is a lit-
tle pore, which probably serves whatever of
oral function is needed, hence it may be called
its mouth. Fig. 121. The evolving of that
pretty cone was not only a beautiful sight to

Fig. 119.

be nutrient processes. canals bb, cylindrical

which adhere closely by

the other side to the cc, triangular spaces. filled with parenchymatous matter. f, dorsal ovary

muscular fibre.

tral ovary sac, or testis. (From Owen.)

look at; but the method of its evolution was a grand thing to see into. As it rose slowly, sack, or testis. 7. Venit was a lengthening truncated cone, with a crater at the upper, or smaller end. And this cone, although without change at the base, kept steadily lengthening at its sides, and narrowing at the top, until at length the truncation, and the crater disappear together— the former in a rounded point, and the latter in a pore. Fig. 122. a, b, c, d.

Fig. 120.

Koleops Anguilla in

repose, the probos

eis withdrawn giv

ing the truncated appearance.

But how could this be done? It should be mentioned that a similar extensile organ in other entozoa has been called by naturalists, from sheer poverty of language, the "proboscis." Hence there is no help for it; and we must use the same inexpressive word. There is a species to which our specimen is allied, which is known by the name Echinorhyncus gigas. Its proboscis, w. en protruded, is of a spherical form, with a neck, or stem below; while at the top of the sphere is a slight projection, around which are several rows, or rings of hooklets. In the centre of the ring that Figs. 117 and 118, a. With

surrounds the top is the oral pore. out regarding form precisely, but rather looking to function, let us liken the neck of the animal to the hand of a glove, and the proboscis to one of its fingers. Suppose that finger to be with

drawn, or inverted. There are two ways in which I can revert the same. I may wish to do so by starting the tip end of the finger, as if I should push it out by pressing the end of a wire upwards, against the under side of the tip, which would in this way come out first or I could, if I wished, push the finger out at the sides. This could be done, for illustration, by having in the hand part of the glove a tube or cylinder of the proper size, down which the glove finger has been neatly pushed, so as to fit snugly against the inner sides of the cylinder. Now if the cylinder be gently pushed upward, the glove finger will ascend on the outside of the cylinder having, as it rises, a crater-like depression at the top. The first of these methods illustrates the propulsion of the pro

Fig. 121.

hooklets.

boscis of Echinorhyncus gigas: and the second one shows the actual evolution of the proboscis of our new entozoon. It is done by the pushing of abductor muscles on the sides of the everting and lengthening cone.

It is noticeable of our species, that when the proboscis is returned into the body, the hooklets are all turned inside the proboscis. Fig. 122, e. This is not true of Echinorhyncus, which keeps its hooklets external to the proboscis, whether that organ is extruded or withdrawn. Figs. 117, 118.

Three real, and easily appreciable distinctions showing the rings of are now pointed out in these two helminths. They differ greatly in the form of the proboscis ; also in the method of propulsion of the same, a method requiring for each differently adjusted muscles; and they differ in the position of the hooklets, when the respective probosces are inverted. It is plain then that our specimen belongs to a new genus.

As to their ordinal relations; both are members of Owen's second Class of the Entozoa, embracing the Sterelmintha, or Solid worms; and both evidently belong to Duvaine's Type iv., Acanthocephala, or Spiny Heads; and to Rudolphi's Order iv., which bears the same name. Now in this order there is but one genus, namely, Echinorhyncus, already mentioned; therefore we put in the order a new genus, to which we give the name Koleops, meaning sheathed-head" and species Anguilla, because found in the common eel.

But the systematist may claim a word. If our name is to be accepted, the giving must respect the methods which Science. regards as Orthodox. Accordingly the following is offered as sufficiently technical to be precise; and yet perfectly appreciable by the popular judgment.

KOLEOPS ANGUILLA Lockwood (gen. et sp. nov.).

Description.- Solid. Form, vermicular, truncated at anterior end, when at rest; when in action the proboscis extended, making with body two cones united at their bases. Length, less than a line when at rest. Thickness at base about one-eighth of length. Proboscis encircled by rings of hooklets external to the cone and pointing backward; when the proboscis is retracted, the hooks are internal to the cone, and point forward. Color tallowy-white, pellucid. At extremity an oral pore.

Habitat. In adipose tissue on the entrails of the common eel, Anguilla acutirostris. Specimen taken from an eel caught in Raritan Bay, near Keyport, N. J. Spring of 1869.

Fig. 122.

d C

a

K. Anguilla; a, b, c, d, showing the progressive projection of the proboscis. e, showing position of proboscis when withdrawn, with the hooklets inside of the cone.

As to the use of those spiny circlets on the proboscis. While they can present but very little obstruction to the penetrating of that organ, the hold thus given the little parasite is very great; indeed it is certain that any attempt to dislodge it must fail, while these grapnels are buried in the tissue, and but for the peculiar muscular functions of the cone-like proboscis, its extraction must be fearfully lacerating, like the withdrawing of an arrow with many barbs. Certain it is that no human device could extract that tiara shaft of spiny rings, from the living tissue, without inflicting an agony beyond expression. When the butcher lifts the meat off his shamble hooks, he does it with a motion suited to the form of the hook, that he may not tear the meat. When Koleops would retract its thorny shaft, the process is begun at the extreme point, which of course is at the bottom of the wound; and how deftly, easily, yea, perhaps painlessly, this is done. Involu tion is begun at that extreme point. The end of the proboscis sinks downward within itself. In fact, it is not a withdrawing in the ordinary sense; for that would make the entire organism move at once, and every barb would tear. It is a gradual involving, beginning at the point, and of course, the first circlet of hooks is by this involving, everted from its hold, and inverted as respects the deepening crater of the now shortening truncated cone. Given the problem, economy of suffering, could a solution more admirable be afforded? It is to be observed that the instant the point of the proboscis reënters the neck on its return into the body, the