32 JOURNAL OF MARINE ZOOLOGY AND MICROSCOPY. 



leaped to meet the rising tide. These leaps ranged from three or 

 four to six feet with a trajectory rising two feet or more — their course 

 always seaward. 



This phenomenon the writer has not observed by day, so cannot 

 say how the movement is performed. 



Then we have on these shores, one Lamellibranch, Galeomma 

 turtoni, which takes up the mode of gastropod locomotion, and with 

 valves set wide open, creeps over the rock with its flattened foot. 



Next we come to the Gastropoda. Here the common land forms, 

 snails and slugs, afford familiar illustration of the usual mode of 

 travel — crawling by the alternate extension and contraction of the 

 muscular foot. This mode is common to all except perhaps the 

 pelagic Heteropoda, for even the pelagic Ianthiria, that carries a 

 float, has the power of crawling ; but a few offer the following 

 additional methods : — 



Strombus, a cousin of the whelks can jump ; some of the same 

 tribe Lachesis, together Avith many of the Opisthobranchs (Aplysia, 

 Doris, Eolis, &c.) have the habit of swimming foot uppermost on the 

 surface of the water. Movement by this means is, of course, very 

 slow and imperfect. A modification of this system, which is better 

 described as a means of transport than of travel, the writer has 

 frequently observed in Eolis, — this is its suspension by means of a 

 thread of mucus, from a globule of the same, which, entangled with 

 air, floats on the surface ; the position of the animal when so sus- 

 pended being always doubled up, hedgehog fashion, with the back 

 downwards. 



Next in order, we come to the Pteropods, or sea butterflies. 

 These Molluscs are pelagic and their means of progression is by the 

 flapping of their large wing-like fins. 



Finally, in the Cephalopoda, we find the highest development of 

 travelling power. The Octopus can propel itself swiftly backward by 

 the expulsion of water from the mantle sac, an average size specimen 

 (say one of two feet in length of body and arms) can propel itself by 

 this means, at a rate of ten or twelve feet per second. It can also 

 swim forward, by a spider-like movement of the arms, with consid- 

 erable speed ; it is in this manner that it usually darts on its prey 

 from its lair. By means of the suckers on its arms it can crawl and 

 climb nimbly over rocks and stones ; and over smooth bottom, by the 

 employment of the tips only of its arms, it can be said to walk. 



Loligo, Omwnatostreplies, Sepia and Sepiola dart backward in- 

 the same manner, and by the same means, as the Octopus, but yet 

 more swiftly, and the two former, at least, swim forward with almost 

 equal ease by means of their fins — the arms in this case being 

 brought together to form a point. 



