1885-86.] Edinburgh Natnralists Field Club. 313 



mon shells are in as great a state of confusion as those of familiar 

 wild plants, therefore the use of the scientific names becomes a 

 necessity when precision is desired. The palates of a few of the 

 univalve Molluscs were extracted in the Club-room the same even- 

 ing, and several specimens are now shown under the microscope 

 by polarised light. The acephalous or headless Molluscs, corre- 

 sponding generally to the bivalves, have, of course, no dental ap- 

 paratus. The palate of the Limpet is very easily extracted, all 

 that is necessary being to make an incision at the head in order 

 to get a hold of the end of the " lingual ribbon," when a gentle 

 pull brings it away gradually in a long roll. Some specimens 

 of the palate of the Limpet were got in this manner nearly three 

 inches in length. When it is noted that the lingual ribbon of 

 the Limpet has 12 rows of teeth, with 160 teeth in each row, or 

 1920 in all, it will be evident that the work done by this chain- 

 saw-like rasping organ must be considerable. The palates of the 

 Whelk and " Buckie " are rather difficult subjects to manipulate, 

 being enclosed in a fleshy tube : this tube must first be extracted, 

 and the integuments of which it is composed carefully cut through 

 with a sharp instrument, before the lingual ribbon can be got at. 



The Crustaceans noticed were tiny specimens of the Common 

 Shore-Crab [Carcinus ???CBMas),the Hermit Crab (^Pagurus BernKardus), 

 and the KcoYTi-&he\V\[Balanus balanoides). The Hermit-Crab, as is 

 well known, never forms a shell for itself, but appropriates that of 

 some Mollusc, changing from one to another to suit the requirements 

 of its own growth, and often ending with the Whelk. Whether it 

 simply appropriates an empty habitation, or coolly makes a meal of 

 the rightful tenant, does not seem to be very clear, although the 

 latter is the more likely method of " taking possession." The Acorn- 

 shells were formerly classed amongst the Molluscs, but now rank 

 with the Barnacles in the class Crustacea, sub-class Cirripedia, — 

 differing from the latter, however, in being sessile, while the Bar- 

 nacles are stalked. The larva of the Acorn-shell, like that, e.g., 

 of the Sponges, is free-swimming ; but the adult undergoes a 

 process of degradation, fixing itself by the head to rocks or other 

 foreign bodies, and then elaborating a calcareous segmented shell, 

 capable of opening at the top for the protrusion of the so-called 

 " hand " — though " foot " would be an equally descriptive term. 

 This foot bears generally six pairs of jointed limbs studded with 

 bristles, and giving the name Cirripedia, or " curl-feet," to the sub- 

 class. The function of the foot is to set up currents in the water 

 by agitating it : food is thus brought within reach, then laid hold 

 of, and conveyed to the interior. A specimen of this interesting- 

 organ, by which, as Professor Huxley says, the animal *' kicks its 

 food into its mouth," is shown under the microscope. Eocks, 

 stones, and Molluscs — principally Limpets — were covered by these 



