ARTIFICIAL REPRODUCTION OF FISHES. 89 



with a microscope of moderate power. Their external 

 appearance is remarkable. The eyes are large and quite 

 well developed; the pectoral fins are also in an advanced 

 stage of development, and in constant and rapid motion, 

 which, I think, in the more advanced stage of the fish, has 

 something to do with its respiration, as they are placed 

 near the opening of the gill covers. The other portions of 

 the fish are quite rudimentary, no other fins being percept- 

 ible, but in their place there is an attenuated margin, or 

 fin-like substance, as on the tail of the tadpole, commenc- 

 ing where the dorsal fin should be, and continuing unin- 

 terruptedly around the caudal and terminating with the 

 anal fin, or rather where it should be. 



This fin-like substance undergoes a constant change as 

 the fish grows older. At fourteen days the dorsal, adipose, 

 caudal and anal fins are plainly seen, but as yet none of 

 them have rays, except the caudal, in which they are very 

 distinct. The rays of the caudal fin are first apparent at 

 the centre, although the general form of the rudimentary 

 tail is very unsymmetrical, the superior lobe being the 

 larger, and the outline not unlike that of the tails of many 

 heterocercal fishes. At this age the fish has more than 

 doubled its former length, the mouth, gills and abdominal 

 viscera are visible, and it manifests a desire to take food 

 by nibbling at the unhatched eggs and pieces of meat 

 placed in the vessel containing them. Its color is now 

 materially changed, being of darkish gray on its back and 

 upper portions of its sides. The sack suspended from the 

 abdomen at this time becomes smaller, and less globular 

 in form, being more contracted anteriorly than posteriorly. 

 The habits of the little creature are also much changed, as 

 it now swims smartly and endeavors to hide whenever dis- 

 turbed. 



Owing to imperfections in our arrangements where we 

 placed the eggs for hatching, accumulations of sediment 

 buried them up, destroying them by hundreds. This accu- 

 mulation was much more fatal when the embryo fish was 



