164 



KNOWLEDGE & SCIENTIFIC NEWS. 



[July, 1904. 



Conducted by F. Shillington Scales, f.r.m.s. 



Collecting Land and Fresh-Wa.ter 

 Mollusca. 



Some useful hints on collectin.s; land and fresh-water 

 mollusca were given some time ago in the " American Journal 

 of Applied Microscopy " (September, 1902), which has now un- 

 fortunately ceased publication ; and I think an abstract of 

 some of these hints may prove of service to those who have 

 not seen the larger article. For land shells a " Ferriss " hoe 

 is very useful. This is made by getting a small light-handled 

 garden hoe, and having the blade cut down at a machine shop. 

 It should be about three inches wide on top, and taper to a 

 sharp point ; the handle being cut off so that it is as long as a 

 walking-stick. This makes a most convenient tool for turning 

 over logs, breaking up rotten wood, and digging around stumps 

 and among dead leaves. A pair of fine curved-pointed forceps 

 is necessary for picking up small species. Small glass bottles 

 should be carried, as the smaller species are apt to get lost in 

 the dirt and slime if put in the same receptacle as the larger 

 ones. It is better not to put the small species in alcohol as 

 they are collected, as they are then killed at once with the 

 animal more or less extended. If put in a dry bottle and left 

 a few hours they will withdraw into their shells, leaving the 

 aperture clear and fit for examination. This is especially 

 necessary with the Piipidac, where the arrangement of the 

 teeth around the aperture is a specific characteristic. For the 

 larger species tin cases of a convenient size for the pocket are 

 most convenient, and specimens from different localities should 

 be kept separate as far as possible. For the fluviatile species 

 a dipper is necessary. This can be made from an ordinary 

 tin one, by removing the bottom and substituting one of fine 

 wire cloth. By removing the end of the handle the dipper can 

 be slipped on to the end of a stick when in use. This is 

 especially useful for sifting the mud and sand from the bottom, 

 where so many small species live, which would otherwise not 

 be found. It will probably be more convenient and thorough 

 to empty the contents of the dipper into a pail, and to carry 

 the whole home before attempting to pick out the shells. 

 The whole mass can then be spread out into the sun to dry 

 and become friable, after which the shells can be easilv 

 separated and picked out, an ordinary reading glass being 

 used if necessary. 



The land species love dampness and darkness, and are, 

 therefore, to be looked for under logs, bark, and leaves in 

 suitable localities. Many species bury themselves in rotten 

 logs, which must be broken up with the hoe. Accumulations 

 of dead leaves around fallen trees, thick grass .and thickets 

 along the margins of ditches and streams will usually repay 

 examination, and should be carefully gone over with fingers 

 and hoe. Coniferous forests are usually quite barren of 

 molluscan life. Nearly every permanent body of water has 

 its molluscs, varying according to its character. Some species 

 are found only in rapid-flowing water, others only in still 

 water and ponds. The low places in woods, which dry up in 

 summer, have a number of species not found elsewhere, and 

 which bury themselves in the mud when it dries. Sand banks 

 in rivers and lakes have many of the smaller species. 



The larger Helices should not be put into alcohol, as this 

 makes subsequent removal of the animal almost impossible. 

 They should be boiled as soon as possible, nearly hot water 

 being useless. A small wire strainer with a long handle is 

 convenient for holding the snails during this process, and 

 saves difficulty in fishing them out, with consequent risk of 

 over-boiling. The time varies according to the size and species, 

 say from 10 to 60 seconds. If not boiled enough the muscular 

 attachment is not loosened, whilst, if boiled too long, the 

 animal is apt to break in two, and thus give trouble in ex- 

 tracting. Only a few should be boiled at a time, as they 

 "pull" easier while warm. When boiled, the animal must 



be slowly and carefully pulled out, too much haste causing it 

 to break, leaving the apical whorls in the shell. The curved 

 points of the collecting forceps serve the purpose, and hooks 

 of different sizes can be made from safety pins tied to small 

 wooden handles. A small fine-pointed dental syringe is very 

 useful in starting the animal, or in case it breaks, in which 

 case soaking in alcohol for twent^'-four hours usually causes 

 sufficient contraction of the remnant to enable it to be washed 

 out by the syringe. After extracting, the interior of the shell 

 must be well syringed. Any mucous must be removed by 

 small sponges attached to fine copper wire, or when dry it will 

 disfigure the specimen. The outside must be scrubbed with 

 a soft nail or tooth brush, no oil or acid being used on any of 

 the land shells. In the small species the animal can be left. 

 After keeping in a dry place for a short time the animal will 

 retire far into its shell, which must then be put into 25 per 

 cent, alcohol for a day or two, and then dried in the air, after 

 which no offensive odour will be left. Either before or after 

 drying the shells can be cleared by shaking in a bottle with 

 fine clean sand. 



In the operculate species, it is desirable to retain the oper- 

 cula, or part of it. These are easily removed from the animal 

 and. after being cleaned, should be put inside the shell, and 

 the aperture plugged with cotton wool. All foreign matter, 

 both inside and outside the shell, must be carefully removed 

 by thorough washing: deposits of lime or oxide of iron on the 

 water species can be removed with oxalic acid, either by im- 

 mersion or brushing with a soft brush, but the operation must 

 not be too prolonged or the shell will be injured. 



The larger bivalves can be well washed, and. if necessary, 

 scraped off with the knife, as soon as found, care being taken 

 not to injure the epidermis. They can be boiled, when the shells 

 will open and the animals be easily removed, or the muscles 

 which hold the valves together can be cut with a thin-bladed 

 knife and the animal scraped out, care being taken not to break 

 the edge of any fragile species. All traces of animal matter 

 must be removed; and, after thorough washing, the valves can 

 be tied together with string until thoroughly dried, but coloured 

 twine must not be used as it is apt to stain the shells. Any 

 incrustations can be removed with oxalic or muriatic acid, but 

 the specimens must be frequently washed and care used. The 

 smaller bivalves are best put into dilute alcohol for a day or 

 two and then dried. If left too long the shells are apt to open, 

 which looks unsightly. 



Both in collecting and cleaning, the specimens from each 

 locality should be kept carefully separated and labelled, as the 

 study of the geographical distribution of the mollusca is most 

 important, and to be of value must be based on accurate 

 work. 



Ground Glass for Diagrams for Lantern 

 Slides. 



There are several photographic methods of making lantern 

 slides of drawings and diagrams, of which the wet-plate pro- 

 cess is perhaps the best : but recently it occurred to me to try 

 a simple method, which has given most satisfactory results, 

 though I do not remember to have seen it suggested elsewhere. 

 All that is necessary is to draw or write with a hard pencil — a 

 6 H for choice — on ground glass squares 3^ X 37, of as finely 

 ground glass as possible, then to flood the ground side of the 

 glass with dilute Canada balsam in xylol or benzol. Cover with 

 an ordinary lantern-slide covering glass, and bind in the usual 

 way. The only precaution necessary is to avoid imprisoned 

 air-bubbles, and this is not difficult when a dilute solution is 

 used. The glasses must, of course, be first carefully cleaned. 

 The result will be that the ground glass is made transparent, 

 whilst the pencil lines become more distinct. 



Royal Microscopical Society. 



May IS, KJ04. The President, Dr. Dukinfield H. Scott, 

 F.K.S., in the chair. The Secretary called attention to two 

 microscopes that had been presented to the Society. One was 

 made by Ladd about 1S64. It had chain movements to the 

 coarse adjustment and to the stage, the motion being particu- 

 larly smooth and free from back-lash. The fine adjustment 

 was effected by a lever hanging from the milled head of the 

 coarse adjustment, by means of which a very slow motion 

 could be given. The other instrument was a small portable 

 microscope, bearing no date, but similar to one made by Cary. 

 Mr. F. W. Watson Baker exhibited a new objective changer, 

 made by Watson and Sons, also a device designed by Mr. W. 



