April 16.
My fish ova in a tumbler has gradually expanded till it is some three sixteenths of an inch in diameter, and for more than a week the embryos have been conspicuously active, hardly still enough to be observed with a microscope. Their tails, eyes, pectoral fins, etc., were early developed and conspicuous. They keep up a regular jerking motion as they lie curved in the egg, and so develop themselves.
This morning I set them in the sun, and, looking again soon after, found that they were suddenly hatched, and more than half of them were free of the egg. They were nearly a quarter of an inch long, or longer than the diameter of a perfect egg. The substance of the egg-shell seemed to have expanded and softened, and the embryo by its incessant quirking elongated it so that it was able to extend itself at full length. It then almost incessantly kept up a vibratory motion of its tail and its pectoral fins, and every few moments it bunted against the side of the egg, wearing it away and extending it, till it broke through. Sometimes it got its head out first and then struggled many minutes before it escaped completely.
It was a pretty sight to see them all rising immediately to the surface by means of the tail and pectoral fins, the first vibrating from one twentieth to one thirtieth of an inch, at an angle of about forty-five degrees, and then, ceasing their motions, they steadily settled down again. Think of the myriads of these minnows set free of a warm morning, and rising and falling in this wise in their native element!!
(Some are still in the egg on the 18th.)
The incessant activity of these minnows, and apparent vigor, are surprising. Already they dart swiftly an inch one side like little pickerel, tender as they are, carrying the yolk with them, which gradually diminishes, as I notice, in a day or two after. They have no snouts yet, or only blunt and rounded ones. I have not detected any general resting even at night, though they often rest on the bottom day or night.
They are remarkably aroused when placed in the morning sun. This sets them all in motion. Looking at them through a jar between you and the sun, a hundred at once, they reflect the colors of the rainbow, — some purple, others violet, green, etc., etc. It is a wonder how they survive the accidents of their condition.
By what instinct do they keep together in a school? I think that the spawn could not have been laid long when I found it April 3d, it was so perfect and the embryo so slightly, if at all, developed. That was a sudden very warm day. In that case, they may be hatched in a fortnight. That appeared to have been a general breeding-place for this species of fish. I looked a good while on the 14th, but could find none near home.
My hylodes in the tumbler will always hop to the side toward the window as fast as I turn it.
We may think these days of the myriads of fishes just hatched which come rising to the surface. The water swarms with them as with the mosquito.
P. M. — To Conantum.
The Rana sylvatica spawn at Hubbard's Grove begins to kick free. This is early. I put some in a bottle, which being shaken in my walk, I find the embryos all separated from the ova when I get home. These are now regular little pollywogs and wiggle about in a lively manner when the water is shaken.
They are chiefly tail and head. They look like the samara of the ash, and in both cases this winged or feather-like tail it is that transports them. I can already see their little feet or fins.
The bodkin-like bulb, considerably grown, in my tumbler and elsewhere, is probably the water-purslane. I see it floating free and sending out many rootlets, on pools and ditches. In this way it spreads itself.
The earliest red maple I can see in this walk is well out, on the Hubbard Bridge causeway. Probably some was yesterday.
I sat a long time by the little pool behind Lee's, to see the hylodes. Not one was heard there; only the skater insects were slightly rippling the surface, pursuing one another and breeding amid the grass. The bottom is covered with pretty proserpinaca.
At length I see one hylodes with heels up, burying itself at the bottom. How wary they are! After nearly half an hour I see one sitting out on a blade of the floating purple grass, but down he goes again. They see or hear you three or four rods off. They are more active toward night.
H. D. Thoreau, Journal, April 16, 1858
I think that the spawn could not have been laid long when I found it April 3d, it was so perfect and the embryo so slightly, if at all, developed. For more than a week the embryos have been conspicuously active, as they lie curved in the egg. This morning I found that they were suddenly hatched, and more than half of them were free of the egg. See April 3, 1858 (“When returning, we discovered, on the south side of the river, just at the old crossing-place from the Great Meadows, north of the ludwigia pool, a curious kind of spawn. It was white, each ovum about as big as a robin-shot or larger, with mostly a very minute white core, no black core, and these were agglutinated together in the form of zigzag hollow cylinders, two or three inches in diameter and one or two feet long, looking like a lady's ruff or other muslin work, on the bottom or on roots and twigs of willow and button-bush, where the water was two or three feet deep. The greater part lay on the bottom, looking like a film, these cylinders being somewhat coiled about there. When you took it up, the two sides fell together, and it was flat in your hand like the leg of a stocking. In one place there were a dozen very large red-bellied and brown-backed leeches in it, evidently battening on it. ); April 7, 1858 ("I brought home t... two kinds of spawn in a pail. ... The other (probably fish) spawn is seen to be arranged in perfect hexagons; i. e., the ova so impinge on each other; but where there is a vent or free side, it is a regular arc of a circle. Is not this the form that spheres pressing on each other equally on all sides assume? I see the embryo, already fish-like (?), curved round the yolk, with a microscope.”);April 14, 1858 (“My Rana halecina spawn in tumbler is now flatted out and begins to betray the pollywog form. I had already noticed a little motion in it from time to time, but nothing like the incessant activity of the embryo fishes. . . .At Ed. Hoar's in the evening.. . .. with his microscope I see the heart beating in the embryo fish and the circulations distinctly along the body.”); April 22, 1858 (“The spawn of April 18th is gone! It was fresh there and apparently some creature has eaten it.”)April 24, 1858 (“I find that my fish ova were not all killed some weeks ago in the firkin, as I supposed, for many that were accidentally left in it have hatched, and they bore the cold of last night better than those hatched earlier and kept in the larger vessel (tub), which froze but thinly, while the firkin froze a quarter of an inch thick last night.”); April 27, 1858 (“I noticed yesterday that again the newly laid spawn at the cold pool on Hubbard's land was all gone, and that in the larger pool south of it was much diminished. What creature devours it? ”); April 27, 1858 (“My young fishes had the pectoral fins and tail very early developing, but not yet can I detect any other fins with my glass. They had mouths, which I saw them open as soon as hatched, and more and more a perch-like head. I think that with Hoar's microscope I detected two dorsal fins such as the perch have. ”);("April 30, 2018 ( I carry the rest of my little fishes, fifteen or twenty, to the cold pool in Hubbard's ground. They are about a quarter-inch long still, and have scarcely increased in length.”); June 16, 1858 ("Looking into Hubbard's Pool, I at length see one of the minims which I put into it. I brought the last here April 30th. It is now a little perch about an inch and a quarter long; it was then about a quarter of an inch long. I can now see the transverse bars a rod off. It is swimming actively round and round the pool, but avoids the quite shallow water of the edges, so it does not get landlocked or lost in the weedy overflowed edges. I put twenty or thirty into this pool in all. They grow very fast, then, at last.”)
I sat a long time by the little pool behind Lee's, to see the hylodes. Not one was heard there; . . How wary they are! See March 31, 1857 (" If you do not listen carefully for its first note, you probably will not hear it, and, not having heard that, your ears become used to the sound, so that you will hardly notice it at last, however loud and universal.. . . The shrill peeping of the hylodes locates itself nowhere in particular.")
My hylodes in the tumbler will always hop to the side toward the window as fast as I turn it. See April 15, 1858 ("Catch a peeper at Hayden’s Pool. I suspect it may have been a female . . . It was a pale fawn-color out of water, nine tenths of an inch long, marked with dusky like this though not so distinctly. It could easily climb up the side of a tumbler, and jumped eighteen inches at once.")
No comments:
Post a Comment