The eggs may be transferred from one vessel to another by means of a glass pipe, the stem of which is closed by the finger. The egg is made to enter the tube by removing the finger. The young fish very soon displays differences of nature and instinct. Some, like the pike and perch, quickly free themselves from the umbilical vesicle and shoot about with great vivacity. Others, as the salmon and trout, retain their provision bags longer, seem more sluggish, and huddle together in dark corners.
Some kinds are so bold and hardy that they require but little care.
The pike, for instance, and the trout, may very soon be put into ponds and rivers, where they will look out for themselves. But others, more delicate and often more valuable, must be kept in artificial basins until they have acquired strength to resist the destructive agencies that await them in the ravenous waters. The basin used at the College of France may serve as a model for the receptacles above named. It has different compartments for the fish of different ages. The wall is built waist-high, that the fish may be conveniently overlooked.