HARDWICKE'S SCIENCE-GOSSIP. 



8i 



lace let into the bottom) to shore and examine our 

 haul. Seven sticklebacks, one newt, numerous speci- 

 mens representing three species of the water-bugs, as 

 many water-beetles, and two pond-snails. We sepa- 

 rate them, and place them in different pickle-bottles, 

 classifying them according to their pacific or bellicose 

 dispositions, for the pond is a microcosm in which 

 species prey and are preyed upon, and the struggle 

 for existence goes on as keenly there as in the larger 

 world it mimics. We take another dip in another 

 part of the pond, and this time besides fish, beetles, 

 and bugs, we get more snails, some fresh-water 

 shrimps and a leech. So we go on dipping and hauling 

 until our bottles are filled, when we retrace our steps 

 along the beautiful lanes to our village resting-place. 

 And now let us overhaul the contents of that tin 

 canister containing the snails, leaving the beetles, 

 newts, &c., to be considered to-morrow. See what 

 a variety there is even among these pond-snails. At 

 a rough glance we can detect at least seven species. 

 You ask what interest attaches to such creatures ? 

 There is a good deal in their life-history that is 

 interesting, if we will only study it. 



If we take one of these snails from the water, the 

 animal immediately withdraws itself completely into 

 the shell, exposing only a small portion of its surface. 

 Put it into the water again, and a great portion of 

 its body will be again protruded. Watch its move- 

 ments. The flat portion of the animal is pressed 

 against the glass and adheres tightly. That flattened 

 body is called the "foot;," but you must always 

 remember that it has not the slightest analogy to the 

 foot of any animal, and the term is therefore a mis- 

 leading one. The term has been in use so long that 

 it would be difficult now to change it, especially as 

 the scientific names of several of the classes are 

 founded on it. If we watch the motion of the foot 

 as it is pressed against the glass we shall notice that 

 this movement is effected by alternate contraction and 

 dilatation of its surface, the result being a series of 

 ripples, commencing from the animal's muzzle and 

 terminating at its further extremity. The head is 

 furnished with a pair of " tentacles," which being 

 very sensitive, act as feelers. At the base of the 

 tentacles are the eyes, and between them, on the 

 under surface, is the mouth. Look at the glass again, 

 and you will see that the mouth is continually open- 

 ing and closing with a regular motion. Its upper 

 margin is armed with a horny mandible and within 

 there is a peculiar light-brown band, which seems to 

 scrape the surface of the glass. This is known as the 

 lingual ribbon or " tongue." It is a most remarkable 

 organ consisting of a very long narrow ribbon, thickly 

 studded with very minute flint hooks which are 

 arranged in a definite order, differing in each genus. 

 By the continual movement of this ribbon the animal 

 scrapes off its food, whether animal or vegetable in 

 nature. 



[To be continued.^ 



THE DIASTOPORID^ : OR THE NATURAL 

 HISTORY OF A FAMILY TYPE. 



By George Robert Vine. 



CAREFUL observers, whenever they have visited 

 the seaside, either for study or for pleasure, 

 cannot have failed to notice, some at least, of the 

 many calcareous incrustations very common on weeds, 

 stones, and dead and broken shells. They may also 



c ct 



Fig. 54. — Zooecia Polypide of Bu- 

 gula plumosa. ph, Pharynx ; 

 oe, CEsophagus ; c, Cardia; cc. 

 Cardiac cavity ; st, Stomach ; 

 ca, Coscal appendage ; i, Intes- 

 tine ; /, Pylorus ; a, Anus ; 

 f. Funiculus. (After Hincks.) 



F'g- S5- — Membra- 

 nip07-a inemhra- 

 nacea. Wall of 

 zooecium. c p. Com- 

 munication plates. 



Fig. ii>.—Memlranipora 7nembra?iacea. 1, Cells covered by 

 membrane, showing "area-orifice," or mouth ; la, Projecting 

 spines : 2, Showing abnormal cells, or what Nilsche called 

 " Tower-zofficia " ; la, Smaller, or less-developed abnormal 

 cell. These peculiar cells are distributed very irregularly 

 over the zoarium. They were first noticed by Ellis, t^-fter 

 Hincks.) 



have toyed with a few of the feather-hke plumes 

 which are sometimes, during severe storms, torn 

 from the deep and cast up with hundreds of other 

 waifs and strays, to rot or bleach upon the shore. 

 Or they may have passed some few hours with the 

 dredging fishermen, and as haul after haul was lifted 

 into the boat, and the contents of the dredge emptied 

 on the deck, they might have picked out some more 

 dazzling plumes that seemed to charm a passing 

 fancy, or appropriated some shell that was more 



