MIGRATION IN ITS BEARING ON LAMARCKISM III 



owners, at a time when money represented much more than it 

 does now. There is a record, which seems trustworthy, of the 

 capture, at a single haul, of ten thousand shad at one of these 

 fisheries, on Fish Island, near Wilkesbarre. Dams across the river 

 have excluded the shad from more than two hundred miles of the 

 course of the Susquehanna, and the profitable fisheries now reach 

 for only a few miles above the boundary of Maryland, while the 

 shad are excluded from many of the best breeding grounds, which 

 are the sandy flats near the shores of streams and the sand-bars 

 which lie in their course. The fishes run up on to these places 

 in pairs, in the early evening, after sunset, and the eggs are 

 thrown into the water while the fishes are swimming about, but 

 they soon sink to the bottom, and develop very rapidly. The 

 average number of eggs is about twenty-five thousand, but a 

 hundred thousand have been obtained from a single large shad. 



Few adult shad escape all the dangers of their journey, and 

 these few are so battered and emaciated that they are of no 

 value as food, and they are unknown in our markets, which are 

 supplied with those which are caught on their way upward. The 

 young fishes remain in the rivers until late in the fall, feeding upon 

 small Crustacea, the larvae of insects, the young of other fishes, and 

 other minute active animals, and they grow to a length of two or 

 three inches by November, when they leave our waters for the ocean. 



The shad is a marine fish which has gradually acquired the 

 habit of depositing its eggs in fresh water, out of the reach of 

 the innumerable enemies which abound on the shoals and sand-bars 

 of the seashore. As the eggs are abandoned by their parents as 

 soon as they are laid, prolonged residence at the breeding place is 

 not necessary, and the shad has thus been able to utilize locali- 

 ties which supply no proper food, and are unfit for prolonged 

 residence. If it were compelled to incubate its eggs and to 

 guard and protect and feed its nestlings like a bird, it would 

 have been restricted to some breeding place where conditions are 

 favorable to a more prolonged residence, and we should then feel 

 something of the same tendency to call its birthplace its true 

 home that we have in the case of birds. We should refer the 

 migration to this place as the starting-point, and should try to 

 find some reason why they spend part of the year elsewhere. 



