160 THE POPULAR SCIENCE MONTHLY. 



what a strange, brush-like appendage ! That fleshy pad is its locomo- 

 tive organ ; and a very funny, but quite pretty contrivance it is. The 

 projected pad is encircled by a frill of cilia, or fleshy hairs, arranged 

 much as the frill is around the large pin-cushion which occupies a 

 place before the mirror of a lady's boudoir. As these cilia play to- 

 gether, the illusion is produced of a revolving wheel ; and, in fact, it 

 is the uni-cycle velocipede of this baby-voyager, with which it must 

 do some traveling in quest of a home, or permanent settlement for 

 life. This frilled organ can be projected and withdrawn in rapid 

 alternations. While being projected, the circular frill expands, thus 

 achieving a very efficient propulsion. And, while being withdrawn, it 

 contracts, or is involved within itself, in this way presenting the least 

 possible resistance to the water. This mechanism, as I understand it, 

 is as remarkable as it is beautiful. It fulfills perfectly, or certainly 

 to a remarkable degree, the conditions of perhaps the most perplexing 

 of the unsolved practical problems in naval science the attainment in 

 union of the maximum power of propulsion and the minimum resist- 

 ance from back-water. 



If we examine a snail, or conch, as typical of the univalve mol- 

 lusks, or shell-fish, we shall find the organs of sense, mouth, tentacles, 

 and eyes, so arranged together as to entitle the object to be known as 

 a cephalate mollusk, that is, one which has a head. The bivalves 

 are not so highly organized, and are acephalate, or headless. It is a 

 curious fact, however, that in the larval state many of these bivalves 

 have eyes, though they lose them as growth proceeds. Although we 

 think it probable, it has not yet been proved, that the larval oyster 

 has eyes. To witness the merry high time of these juveniles, it would 

 seem that they both have eyes .and are bound to use them, too, in 

 seeing something of the world ; for, as if eviction entailed neither dis- 

 grace nor inconvenience as with certain bipedal juveniles under 

 pupilage oil* they go in the wildest glee imaginable. But the gay 

 frolic is soon over. A few settle down, like the old folks, to a sober 

 life. Alas ! it is with the rollicking young oysters as with many 

 other young people this wild-oat sowing yields a fruitful but peril- 

 ous harvest. Of each million that enter upon this dissipation, but a 

 few hundreds, at the most, survive. Many have been devoured by 

 hungry enemies lying in wait, and many went to sea, and, unable to 

 return, perished miserably. The survivors attach themselves to any 

 thing that offers an anchorage ; and these are called " spat." Fig. 1 

 contains five groups of oysters of as many different ages, all of which, 

 by a professional oysterman, would be called " spat," excepting the 

 three largest at the top. The attachment is made at the lower valve. 

 And, now having wound up its giddy career, what was done with the 

 velocipede ? In plainer words, what is to become of the locomotive 

 pad, for which it has no further use ? It begins to disappear not by 

 atrophy, however, nor is it sloughed off in any way. Herein appears 



