HARD WICKE ' S S CIE NCR- GO SSI P. 



103 



when or where it was first breathed to him, for he has 

 known it for some years. 



The application of soap for the above purpose 

 seems to have suggested itself to Dr. Stolterforth, 

 who says (Journal of the Quekett Microscopical Club, 

 August iSSo, p. 95) that the idea occurred to him 

 when trying to clean some of the Welsh deposits. 

 His viodus operandi is as follows : I place in a test- 

 tube (6 in. long by i in. wide) a portion of the earth 

 or mud about \ in. in depth, and pour in water until 

 the tube is a quarter full j into this I drop a piece of 

 yellow soap about the size of a small pea, and then 

 boil gently over a lamp. When the diatoms are clean 

 I fill up the tube with water and let it stand, then 

 wash in the usual way until all trace of the soap is 

 removed. Dr. Stolterforth omits all other cleaning, 

 either with acids or alkalis, and he finds that soap 

 alone is all that is necessary for all kinds of fresh or 

 salt-water deposits. E. H. Grifiiths, Esq. ("American 

 Monthly Journal of Microscopy," April 1880, p. 88) 

 also advises the use of soap (which he says he learned 

 of Professor Smith) and afterwards, if necessary, 

 nitric acid and carbonate of potash to bleach. 



I have myself tried this method of cleaning, and 

 can to a certain extent endorse what has been pre- 

 viously stated as to its use. I first tried it on a 

 subpeat deposit from New Zealand, which, however, 

 required acid treatment before it was sufficiently clean 

 for mounting. I also tried it on a recent fresh-water 

 gathering from the same locality with similar results. 

 My next trial was upon some Peruvian guano. I 

 found that the soap very much assisted in getting rid 

 of a lot of colouring matter, and materially reduced 

 the quantity of the crude material. I may here remark 

 that, after pouring off all that did not subside in one 

 hour, I again boiled in soap and water, which further 

 reduced the quantity ; but the residue was totally unfit 

 for mounting until further cleaned with nitric acid 

 and chlorate of potash, and a final wash with liquor 

 ammoniae. On the marine deposits, such as those from 

 Virginia, California, Barbadoes, &c., soap seems to 

 have but little if any effect. 



To those who may be desirous of trying the soap 

 process the following hints may be useful. 



1st. Carefully avoid hard water. 



2nd. Use the best yellow soap (the ordinary soap 

 often contains oil). 



3rd. If soap is used after the acid, remove all traces 

 of the latter with soft or distilled water. 



4th. Dissolve the soap in the water and pour it on 

 the material, so as to make sure that no portion of it 

 remains undissolved. 



The soap process does not seem to possess (in my 

 opinion) any advantage over liquor ammonise in 

 eliminating flocculent matter. The preliminary boil 

 in soap and water, by getting rid of a portion of the 

 non-diatomaceous material no doubt reduces the 

 quantity of acid required, but it will not supersede 

 the use of it. F. Kitton. 



NOTES ON POND-SNAILS {LIMN^A). 



TO be able to see with the eye the beginning of a 

 living creature from the very embryo, is one 

 of the most amazing and instructive sights the 

 powers of the microscope can reveal, and one which 

 opens the mind to wonder and admiration, giving 

 the observer an immense field for thought and con- 

 jecture. Now that the spring is on, this can be seen 

 by any of your young readers microscopically in- 

 clined, who use the instrument as a means of learning 

 more of the world they live in, and who are fond of 

 studying its smaller and more insignificant inhabi- 

 tants, which some people, who " care for none of these 

 things," would pass by as worthless and beneath 

 their notice. By searching any freshwater stream 

 or pond they will be sure to find, without much diffi- 

 culty, attached to the weed at the edge, or to the stem 

 and leaves of plants growing in the centre, a lot of 

 small oblong masses of a transparent jelly-like sub- 

 stance ; these are the ova sacs of the Limnaea or fresh- 

 water snails. All they have to do is to take these 

 home and keep them in a shallow trough, convenient 

 for placing on the stage of the microscope at any 

 moment. At first when examined this gelatinous 

 substance will be found to contain a number of small 

 oval-shaped eggs filled with a perfectly clear homo- 

 geneous substance, with a small dark speck in each 

 (the nucleus); if this is watched from day to day, the 

 development is extremely interesting. The nucleus 

 is seen to enlarge gradually up to the eighth or 

 ninth day, when the embryonic animal commences 

 to move in the interior of the ova in a rotatory 

 manner ; in a day or two more the rudimentary eyes 

 can be observed, and also a strong ciliary action, 

 close to the edge of the egg, very like the fringe of 

 cilia on a common vorticella, by which I suppose a 

 motion of the fluids in the egg are kept up. The 

 embryo still enlarges until it breaks through the shell 

 and comes forth a living animal — the whole process 

 of development occupying about a month. I have 

 only given a rough sketch, the minutiae of it would 

 occupy too much valuable space. I only hope it will 

 be the means of directing some attention to these 

 animals. 



The egg walls being so transparent, there is no 

 difficulty in watching the whole operation. The 

 pleasure derived from a short study of the embry- 

 onic life of those freshwater molluscs well repays the 

 time spent upon them, and can be obtained at a 

 minimum of trouble. — P. B. 



Skylark.— One day in March this year, I saw 

 and heard a lark [Alaiida arvensis) singing while 

 settling on a heap of ashes in a market-garden near 

 this town. The song was prolonged, as it is when 

 this bird is soaring. I have noticed this habit of the 

 skylark before.— /Av;;:;' Lamb, Maidstone. 



