174 



HARD WI CKE ' 6" S CI EN CE-GO SSIP. 



flattened, yellow, seated on radiating, branched, intri- 

 cate flocci. 



On various decaying substances, tan, &c. This is 

 the fully-developed form of Aspergillus glaucus. 



A word in conclusion as to mounting these fungi 

 for the cabinet. They seem to be best put up in 

 shallow varnish cells, filled with glycerine and water. 

 Deane's gelatine, so invaluable a medium for most 

 other vegetable preparations, is too viscid, the appen- 

 dages enclosing a myriad of air-bubbles, which in 

 gelatine are almost impossible to get rid of. More- 

 over, without a cell the covering-glass presses too 

 closely and is apt to cause the perithecium to rupture 

 from pressure. The modus operandi is a simple one. 

 When the cell is ready, filled with dilute glycerine, 

 scrape the leaf on which the parasite grows with a 

 sharp knife, which will remove a good number of 

 perithecia ; push gently into the mounting fluid, and 

 finish as in any other wet mounting. 



ON TANKS FOR THE BREEDING AND 



MAINTENANCE OF MICROSCOPIC 



ORGANISMS. 



IN the May number of Science-Gossip a corre- 

 spondent seeks information on the subject of the 

 establishing and management of tanks or receptacles 

 for the preservation and development of microscopic 

 organisms. To the microscopist it is a matter of some 

 importance, and one of which there seems to be no 

 record of any valuable, reliable, or actual experience. 

 The subject is of deep interest, and possibly your corre- 

 spondent and readers generally may consider the few 

 following notes, founded on many years' experience, 

 worth attention, more especially as the mode of esta- 

 blishing a permanent tank, containing microscopic 

 plants and animals only, is not generally studied or 

 even understood, the popular idea being that a collec- 

 tion of organisms found in the water of a rich pond 

 turned into a glass vase will at once afford and possibly 

 maintain and develop objects of interest and curiosity 

 for immediate examination, when in fact a keeping 

 or breeding tank requires many months, sometimes 

 years, for the perfect development of its contents. 

 No one could hope to raise the most interesting 

 features (to a microscopist) of a garden in a few days. 

 Time and the seasons are required to develop the 

 mosses, lichens, fungi, and obscure growths to be 

 found on good rockwork : the same prolonged causes 

 developing life, apply (perhaps in a lesser degree) 

 to the microscopist's breeding-tank ; it is a question of 

 patience. As a notable instance, the statoblasts of the 

 most beautiful of fresh-water polyzoa (Lophopus) are 

 frequently found in early autumn in the muddy sedi- 

 ments of ponds, rich in microscopic life. This 

 sediment, transferred to a well-ordered perfectly- 

 balanced tank, will produce the young polyps freely in 



the spring, and there are numerous instances of a 

 similar character where time is a factor in the appear* 

 ance of microscopic life in captivity. 



In the practical management of these tanks two 

 points are of essential importance : first, size, and, as 

 regards light, position ; secondly, the internal arrange- 

 ments, and the character, requirements, selection, and 

 management of the occupants, both vegetable and 

 animal, so as to ensure development and repro- 

 duction. 



The shape and place of occupation of the receptacle 

 claim the first attention, and are of great importance. 

 It is true that ordinary glass jars or vases of various 

 sizes ai - e continually used with more or less success in 

 preserving living objects, but they utterly fail as 

 breeding or developing places : their circular forms 

 impede observation ; again, their portability causes 

 them to be frequently shifted into different aspects, 

 which is fatal to steady development. They are too 

 often placed in positions overwhelmed with light, 

 when they rapidly become choked with filamentous 

 algae, destructive to the preservation of the higher 

 microscopic forms. The proper adjustment of light 

 seems to be the touchstone of success in the cultivation 

 of organisms, both animal and vegetable. The 

 vitality of some water-plants, under what would seem 

 the most unfavourable, but, as it turns out, the most 

 favourable circumstances, is very singular ; the merest 

 fragment of Nitella will live for months in a wine- 

 glass of water, or even in a small test-tube, if kept in 

 a cool and rather dark place, but abnormally excited 

 by exposure to sun, light, and heat, it soon fades and 

 collapses. This is a lesson of importance, as un- 

 doubtedly the same influences affect minute animals. 



The tanks for the purpose in question should not 

 be too large ; a convenient proportion, and meeting 

 all contingencies, is a vessel made of narrow iron 

 frame-work, glass sides and ends, with slate bottom, 

 measuring fourteen inches wide, fourteen deep, and 

 twenty-eight inches in length. Two or more of these 

 tanks are necessaiy : two are indispensable, as there 

 is a marked difference in the character of the occu- 

 pants of a tank facing a wall with only side light (and 

 no sun) and another facing a window (north aspect) 

 with occasional rays of setting sun. Besides these 

 permanent and larger receptacles, sauare glass vases 

 or vessels, such as are sometimes used for galvanic 

 batter}- cells, of the capacity of three pints, are very 

 valuable to contain objects dipped from the larger 

 tanks for special observation on the study table. 



The permanent tanks should be placed in position 

 and never again moved. A good aspect is north- 

 east, fronting a window catching an hour's early 

 morning sunlight, but a better is against the wall of 

 a room or hall with a full side-light, and no sun; 

 the difference between the life contained in tanks 

 placed in such positions is strikingly apparent. Of 

 the internal arrangements anything approaching the 

 idea to make it "pretty" should be studiously 



