clams, like sardines in a box, even 

 though there were but a few pairs to 

 start with. There is not food enough, 

 and there are plenty of other hungry 

 creatures ready to grab for the little 

 there is. Clams are inactive and spend 

 most of their lives in the same spot, 

 unless strange fate orders otherwise as 

 it actually did in the case of our pair. 

 If mother clams sent out their numerous 

 progeny into the world of waters with 

 only their blessing, and they settled down 

 about the paternal home, the race would 

 soon become extinct. Currents of water, 

 indeed, might carry some away, but they 

 would be taken always down stream. 

 Mother nature, or in cold scientific lan- 

 guage, natural selection, has given each 

 tiny one a chance to save himself and his 

 race from extinction. If he can use the 

 little hooks upon his shell with which he 

 has been prophetically furnished, he may 

 get out into the world and escape the 

 competition with his own brothers and 

 sisters. The case is desperate and he 

 resorts to questionable methods. 



A fish passed by that day they were 

 ejected from their home, and he whisked 

 his fins against that animated heap of 

 sand grains at the bottom of the stream. 

 Here was the opportunity of a life-time. 

 Some few of the enterprising ones, 

 among them our pair, caught on by their 

 hooks, and away they were carried up 

 stream. And so good-bye to home and 

 family. For ten weeks they traveled and 

 saw the world. Fortunately their unwil- 

 ling host escaped unscathed the hooks 

 of anglers and the foes that beset him on 

 every side. Our voyagers prepared to 

 settle down and make themselves as com- 

 fortable as possible, like true travelers. 

 The irritation of the skin of the fish by 

 their little hooks caused outgrowths to 

 form in which they became encased. 

 They next exacted not only free trans- 

 portation, but free board as well ; the 

 body juices of their host being absorbed 

 by the mantles of the tiny passengers. 

 Speaking plainly, they were just para- 

 sites at this stage of their existence. But 

 they showed that their nature was not 

 wholly depraved, for they were getting 

 ready to get an honest living. A digest- 

 ive canal was forming — the muscles and 

 foot, the feelers or palps about the 

 mouth, and outfoldings near the mantle, 



the rudiments of gills. The byssus and 

 the sense organs disappeared. One day 

 they dropped from their host, gave up 

 the parasitic life, settled down in the 

 sandy bottom of the stream to be honest, 

 sober-minded, stay-at-home clams for the 

 rest of their lives, and proceeded to take 

 on fully the form and habits of their 

 parents. 



Of great importance now were their 

 thick shells, for they protected them from 

 most of their enemies. At first they were 

 very tiny, but as time went on, layer 

 upon layer of lime was added till they 

 grew broad and thick, with a beautiful 

 mother-of-pearl lining and a brown 

 horny outer skin which rendered them 

 inconspicuous tO' the casual passer-by. 

 The two shells were attached at the top 

 by a hinge ligament, which being always 

 on the stretch, could spring them apart. 

 Little teeth inside fitted into each other 

 and kept the valves from slipping. One 

 end grew broader than the other. This 

 was the anterior end, though strange to 

 say, it was buried in the mud. At either 

 end was a big muscle running from shell 

 to shell to close them. When the occu- 

 pant was undisturbed the shells were 

 opened a little to allow currents of water 

 to enter. But let an unwelcome guest 

 appear, and quickly the shell closed with 

 the force of a vise. Bird's beaks and 

 feet are known to be caught thus some- 

 times, and the fingers of curious stu- 

 dents. The clam is firm, if not always 

 reasonable, and it takes strong persuasion 

 to make one relax his grip. When dis- 

 turbed, then, or out of water, the shells 

 close ; if they are found quite open the 

 animal is dead, the muscles have relaxed. 

 The thin, delicate mantle lines each shell. 

 At the posterior end, the end sticking out 

 of the mud, the edges of the mantle are 

 slightly attached to form two slits, called 

 siphons. In some marine cousins of our 

 fresh water clams these are grown out 

 intO' long tubes which reach to the sur- 

 face while the animal burrows far down 

 in the ooze. Little papillae border these 

 slits, and they are sensitive to light. 

 Through the lower of these slits or 

 siphons water currents come in, brought 

 by the waving of multitudes of minute 

 hairs called cilia, growing in the gill cav- 

 ities. The water circulates through the 

 gills, up to the mouth end of the body, 



308 



