lo(5 Mailers Archie fur Anatomie, Sfc. 



cordingly took a flat shallow dish, the bottom of which was covered with 

 paper, and filled it with lake water. Some more fecundated ova were 

 then placed in it, so that they did not come in contact with one ano- 

 ther. In five hours he again remarked that some had become opaque 

 on one side, and in twenty-four hours the same thing had occurred to 

 nearly all. Some few, however, remained transparent, and these he 

 raised gently from the dish, by means of the paper that was under them, 

 and transferred them to glasses of water for farther observation, placing 

 eight or ten in each ; in six or seven hours after this operation, he saw 

 by means of a microscope that the embryo had begun to move, and in 

 twenty-four hours (fifty from the moment of fecundation) the young 

 fishes burst through their envelope. The experiment was again repeat- 

 ed in order to ascertain whether the ova of fishes undergo similar 

 changes to those of the Batrachians (vide Analysis of Muller's Archiv at 

 p. 292,) and half an hour after the eggs had been placed in the dish, 

 he lifted out those which remained transparent, and transferred them to 

 glasses as before. It was now his object to destroy the vitality of some 

 of them at each stage of their development, in order to examine the pro- 

 gress that had been made, at leisure, and for this purpose he dropped 

 into the water four or five drops of a mixture of one part of nitric acid 

 and eight parts of water, which had the desired effect. This was appli- 

 ed at intervals of fifteen minutes during ten hours, and the following are 

 the results obtained : Soon after the application of the milt, the ovum 

 of the tench loses its spherical form, and swells out into the form of a pear. 

 At the point where this swelling begins it is surrounded with a cluster 

 of microscopic globules, which before were spread all over its surface. 

 In half an hour the pear-shaped excrescence is divided into four glo- 

 bules ; these in a quarter of an hour more are subdivided into eight, and 

 in a similar period into thirty-two, still remaining clustered together 

 on the top of the egg. In another half hour more globules appear, 

 decreasing in size as they increase in numbers, till at length, from their 

 minuteness, the part of the egg to which they are attached becomes 

 almost as smooth as when they were undeveloped. The embryo fish 

 now becomes discernible in the form of a whitish semitransparent speck, 

 which is the rudiment of the vertebral column. The organization of the 

 skin then gradually proceeds, and the embryo increases in length, coiled 

 round the yolk, till the head becomes perceptible. In forty hours from 

 the fecundation, the embryo tench first gave signs of motion, and at 

 most, twelve hours later, it had freed itself from the skin of the egg. 

 The fish is then two lines in length, and the blood has already acquired 

 its natural colour. For some hours after leaving the egg, the young fry 

 appeared stupified ; they he on their sides and are unable to swim, until 

 the swimming bladder is developed, when they immediately assume 

 their proper position and their natural activity. The intestines are not 

 fully developed until seven days after leaving the egg, when they begin 

 to feed voraciously, and exclusively upon animal substances. The fry 



