I see the heart beating in the embryo fish.

April 14. 

Rains still, with one or two flashes of lightning, but soon over. 

The yew plucked yesterday blossoms in house to day. 

P. M. — Up Assabet. 

The river is a little higher on account of rain. 

I see much sweet flag six or eight inches long, floating, it having been cut up apparently by musquash. (The 17th I see much of the sparganium cut up close to the bottom along a musquash-path at the bottom of a meadow where there was one foot of water.) 

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.  

I find no suckers’ nests yet. There has been no rise of the river of any consequence. 

At Ed. Hoar's in the evening. I look at one of his slides through a microscope, at the infusorial skeletons of the navicula and dumb-bell infusoria etc. etc. with his microscope I see the heart beating in the embryo fish and the circulations distinctly along the body.

H. D. Thoreau, Journal, April 14, 1858

The river is a little higher on account of rain. See April 14, 1855 (“The river has been steadily rising since the first of April.”)

My Rana halecina spawn in tumbler is now flatted out and begins to betray the pollywog form. See April 7, 1858 (“ Putting some of the Rana halecina spawn in a tumbler of water. . . .”); April 17, 1858 (“The Rana halecina spawn in tumbler begins to struggle free of the ova”); April 18, 1858 (“Put some R. halecina spawn which has flatted out in a ditch on Hubbard’s land.”);April 19, 1858 ("I find that my Rana halecina spawn in the house is considerably further advanced than that left in the meadows.")

I see the heart beating in the embryo fish and the circulations distinctly along the body. See April 7, 1858 (" I see the embryo, already fish-like (?), curved round the yolk, with a microscope"); April 16, 1858 (" 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.")

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