200 



H A 11 D W 1 C K E' S SCIENCE- GOSSIP. 



[Sept. 1, 1868. 



notched on alternate sides, in these notches are 

 placed the sessile flowers — one in each. The outer 



Fig. 205. 



glumes are parallel, hard, and stiff, with prominent 

 green ribs. Beneath each flower is a joint, at any 



Fig. 206. Lep turns incurvatus. 



of which the stem readily breaks. Young botanists 

 visiting the sea-side will do well to look out 

 for it. A careful examination will repay the 

 trouble. It occurs in the marshes here somewhat 

 sparingly. 



St. Mary's Vale, Chatham. H. 



PALATES OE MOLLUSCS. 



Land and Fresh-water. 



rpHE mouth in Gastropods is armed with an upper 

 -*- horny jaw, and adherent within the cavity is 

 a horny muscular tongue, which is a 'mechanical 

 organ for the attrition of the food. This Ungual 



ribbon or tongue, as it is termed (often, but 

 erroneously, pallet), is covered by more or less 

 regular quadrangular plates, carrying erect amber- 

 coloured and glossy teeth of extreme tenuity, 

 which are directed backward. This tongue acts 

 in concert with the horny jaw, the one holding 

 and the other raspiug the vegetable food into the 

 mouth. 



As the Ungual ribbon is such a pretty and inter- 

 esting object for examination with the microscope, 

 and as it plays so important a part in the economy 

 of all snails and slugs, land, fresh-water, and 

 marine, and also because the teeth vary'in number, 

 in arrangement, and in ornamentation in the different 

 genera and species, I will now give a method of 

 preparation, and will also point out, in its proper 

 place, the value in a systematic arrangement of the 

 species of these objects. 



The tongue forms the floor of the mouth, and the 

 front part, which is the only part in use, is fre- 

 quently curved or 

 bent quite over, 

 and its teeth arc 

 often broken and 

 blunted ; the 

 hinder portion descends obliquely behind the 

 mouth, and its edges are united to form a tube, and 

 enclosed in a membranous sheath, which opens 

 gradually as the part is brought forward to replace 

 the worn portion. 



The most simple plan to prepare these as micro- 

 scopic objects is to boil the head of the mollusk in 

 a solution of potash in a test-tube, by which all the 

 parts, with the exception of the tongue and jaw, are 

 dissolved : care must be taken to thoroughly wash 

 the tongue before mounting. 



The most instructive method is doubtlessly that 

 of dissection ; but certainly, when we have some 

 of our minute snails to deal with, that of mace- 

 ration will be a great saving of time and patience. 

 The head should be pinned down in a gutta-percha 

 trough containing water enough to cover the part ; 

 the floor of the mouth may be laid open by pass- 

 ing the lower point of a pair of scissors into the 

 mouth, and cutting upwards ; now pin back the 

 severed portions, and by the aid of a lancet or 

 needle, work out the lingual apparatus. The 

 ribbon should be cleaned by washing with a camel's 

 hair brush, or by soaking in potash-water ; if the 

 latter, wash the tongue well before mounting. The 

 preparation may be mounted in glycerine, or if 

 intended as an object for the polariscope, it should 

 be mounted in Canada balsam. 



The length of the lingual ribbon is short in Palu- 

 dina, but is of varying length for different species ; 

 in the marine limpet it is longer than the whole 

 animal. The teeth are distributed in straight longi- 

 tudinal rows, and in transverse rows, which are 



