Part 36 (2/2)
”It is doubtful,” was the reply, ”but their value lies so largely in their use for mother-of-pearl in the b.u.t.ton industry, that their food value would be of only secondary importance, unless they could be pickled or canned, as is done sometimes with the sea-mussels. But, Colin,” he added, ”if you think that the mussel doesn't sound an interesting subject, let me tell you that I think it is, in itself, one of the most interesting creatures in the water. Its life history is astounding, and there are scores of problems yet to be worked out. Read this,” he added, handing the lad a Bulletin of the Bureau; ”it has only just come out, and if I have judged you rightly, you'll come here on June fifteenth so eager to get to a mussel-bed that there will be no holding you!”
[Ill.u.s.tration: CLAMMING ON THE MISSISSIPPI.
_Courtesy of the U. S. Bureau of Fisheries._]
[Ill.u.s.tration: BARGE-LOADS OF MUSSELS FOR THE MOTHER-OF-PEARL INDUSTRY.
_Courtesy of the U. S. Bureau of Fisheries._]
Two hours later, the Deputy Commissioner, leaving the office for the day, started on his walk home, going through the park in the direction of the Smithsonian Museum. On his way he was surprised to see Colin sitting on a bench near the Fisheries Building, absolutely engrossed in a gray, paper-covered folio. Dr. Crafts recognized it as the Bulletin he had given the lad early in the afternoon, and he laughed aloud at the boyish impatience which had made it impossible for Colin even to wait until he got the book home. The Deputy Commissioner had to speak twice before he was heard.
”Well, Colin,” he said, ”are you learning it off by heart?”
The boy jumped up as soon as he saw his friend, fairly stuttering with all the questions he wanted to ask.
”I've got to go home,” the Deputy Commissioner said, when Colin stopped to take breath; ”and you've put queries enough to keep a staff of men answering for a week! Didn't I tell you that there's a world of work to be done over the mussel? But if you like to walk along, why, I'll tell you anything I can.”
”Thanks, ever so much,” the boy said; ”but what puzzles me in this Bulletin is the mussel's marsupium, or pouch. Has a fresh-water mussel really got a pouch like a kangaroo?”
The Deputy Commissioner pushed his hat back over his forehead.
”Colin,” he said, ”you have a knack of putting questions in the most awkward fas.h.i.+on. I suppose, in a way, the answer is 'not quite,' because in the kangaroo, the baby is almost completely formed when it is placed in the pouch, while in the mussel, only the egg goes there. The word 'marsupium' was what threw you off. What really happens is that the egg pa.s.ses into this pouch or pocket in the gills, and is there fertilized as the current of water flows in and out over the gills.”
”And it stays there until it has a sh.e.l.l of its own, doesn't it?” asked the boy.
”It does,” was the reply.
”Well,” said the eager questioner, ”if it has a sh.e.l.l and is able to look out for itself, why doesn't it? Yet the book says that it always attacks a fish and lives as a parasite for a while.”
”It doesn't attack a fish, Colin,” the other answered; ”it only fastens on to one. Besides which, although the mussel has a sh.e.l.l, it isn't able to look out for itself. There is a change of form while it is fastened to the fish.”
”But doesn't it hurt the fish?”
”Not permanently. It causes a local sore or a cyst, like the tiniest kind of a blister, in the middle of which the larva of the mussel is safely curled up and stays there until fully developed. Then the cyst breaks, the mussel drops out, and the tiny wound heals rapidly. Even a small fish, four inches in length, can carry five hundred of these little creatures on its fins and in its gills without serious injury.”
”Suppose it can't find a fish?”
”That's the end of the mussel, then! There is one kind of mussel that develops without going through the parasite stage, but it is not as common as the others. Curiously enough, the only way to raise the mussel artificially is by means of parasitism on the fish. As you read there, it is a simple matter to get these tiny creatures from the 'pouch' of the mother mussel, put them in an aquarium with some fish, and keep the water stirred up. In a few minutes the larvae will have fastened themselves on. It is wise to keep these fish in a hatchery for a month or so and then simply release them; when the mussels are ready they will drop off, and a new crop of mussels is on the way. By this means you can start them without much trouble in rivers and streams where there were none before, so that you see what chances there are for the development of the industry.”
”Are all mussels equally good for making mother-of-pearl?”
”No,” was the reply. ”There are two chief commercial varieties, of different species, one larva having a hook on the sh.e.l.l, so that it can attach to fins or tail, the other being smaller and without hooks and making its way into the gills. But you'll go into all that when you get to Fairport, and even after you have worked at mussels all summer there will be a lot of problems you won't have touched. Don't forget now, the fifteenth.”
”Never fear, Dr. Crafts,” Colin answered; ”I won't forget. I wish it were here now.”
Time did not hang heavily on the boy's hands, for he was interested in all phases of fis.h.i.+ng, and spent a couple of weeks on a trout stream in Northern Maine, not only catching the fish, but--as he had been advised--making notes of any peculiarities he saw in those he caught.
Many stories had been told him of the finding of new species by young investigators, and he was amazed to see what wide differences existed in fish of the same species.
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