The salmon is a conspicuous example of those fishes which can be artificially propagated. The eggs of the salmon are large, firm, and separate from each other. If the female fish be caught when the eggs are ripe and her body be pressed over a pan of water the eggs will flow out into the water. By a similar process the milt or male sperm-cells can be procured and poured over the eggs to fertilize them. The young after hatching are kept for a few days or weeks in artificial pools, till the yolk-sacs are absorbed and they can take care of themselves. They are then turned into the stream, where they drift tail foremost with the current and pass downward to the sea. All trout may be treated in similar fashion, but there are many food-fishes which cannot be handled in this way. In some the eggs are small or soft, or viscid and adhering in bunches. In others the life-habits make artificial fertilization impossible. Such species are artificially reared only by catching the young and taking them from one stream to another. To this type belong the black bass, the sunfish, the catfish and other familiar forms. FOOTNOTE: [16] The author wishes to call the attention of teacher and student to the plan (referred to in the Preface, page v) adopted in writing the directions for the dissections. The sequence of the references to the various organs depends on the actual course of the dissection, and not upon the association of organs in systems. And the directions are so much condensed that they are hardly more than a means of orienting the student, leaving him to work out independently, or by the aid of more detailed accounts (sometimes specifically referred to), the details of the dissection. CHAPTER XXV BRANCH CHORDATA (_Continued_). CLASS BATRACHIA: THE BATRACHIANS The structure, life-history, and habits of the garden-toad (_Bufo lentiginosus_) have already been studied (see Chapter II and Chapter XII). OTHER BATRACHIANS.