iLiRCn IC, 1883.] 



♦ KNOWLEDGE ♦ 



1C3 



Nature's work — the human trunk — can bear without 

 giving way ; but nothing more. It suggests also that, 

 whatever the lady may think she remembers, she was more 

 comfortable when less tightly laced. — R. P.] 



PLEASANT HOURS WITH THE 

 MICROSCOPE. 



By Hexrt J. Slack, F.G.S., F.RM.S. 



AN interesting train of thought may be suggested to the 

 microscopist who will pay some attention to the tool 

 and implement-making processes which occur in many of 

 the lower organisms, and which result in objects wonder- 

 fully like the productions of human invention and skill. 

 The objects alluded to are called tools and implements for 

 want of more appropriate terms. They are exactly like 

 what men so designate, although their uses in the economy 

 of the creatures forming them are different A good slide 

 or two of sponge spicules, obtainable from any vendor of 

 microscopic preparations, afford excellent illustrations. 

 Sponges consist of a very soft animal matter, supported, 

 •except in one family, by a horny, flinty, or chalky frame- 

 work, as the case may be. The two last especially are 

 atrengthened by spicules of various shapes, and also pro- 

 vided with spicules of defence, which make them incon- 

 Tenient objects for their enemies to bite. That a soft 

 animal should be able to take from the water in which it 

 dwells calcareous or silicious matter, and deposit it in con- 

 ▼enient forms, is not in itself an unusual or very striking 

 circumstance ; but we are astonished when we find little 

 models of hooks, spears, tridents, grappling irons, caltrops, 

 and many other tool and implement sorts of things. 



Amongst the most curious are the fish-hook spicules of 

 Hyviedesmia Johnsonii. Each shank carries two hooks — 

 one at each end — and they project at right angles to each 

 other, or near it. The hook part has an extremely sharp 

 internal knife edge, a very acute point, and at the base of 

 the blade a little notch which acts as a barb. The variety 

 to be found in different genera of sponges is consideraVile, 

 and it is marvellous that organic processes of growths 

 should in many instances prefigure human inventions. In 

 the sponge family they cannot properly be called either 

 tools or implements ; they are strange simalacra, and 

 though each form must have special reference to the life- 

 processes of the creature, they have not the same special 

 adaptation to its habits that we find in the apparatus with 

 which insects are furnished. We can scarcely imagine that 

 a sponge whose defensive spicules are like caltrops can be 

 better or worse provided for the battle of life than one 

 with fish-hooks ; but when we come to the tools and im- 

 plements of insects, we see a close adaptation to peculiar 

 wants. 



The mouths of insects exhibit a wonderful variety of 

 modifications, and in many cases, if the early races of men 

 had been aVjle to see them, they might have found i)attems 

 of the most useful tools. The subject of these mouths is 

 too large and too important to be spoilt by a casual notice ; 

 but it may be said with Haeckel, "the heads of (lies 

 universally possess, beside the eyes, a pair of articulated 

 feelers, or antenna;, and also three jaws on each side of the 

 mouth. These three pairs of jaws, although they have 

 arisen in all flies from the same original basis, become 

 changed by different kinds of adaptation to very varied and 

 remarkable forms in the various orders." Chewing, suck- 

 ing, biting, and licking, are the functions which the mouths 

 of different insects are modified to perform. The mouth 



organs, as prepared in the slides generally sold, are all 

 flattened and squeezed together in Canada balsam, and in 

 that condition are far less instructive and intelligible than 

 if mounted in fluid, or examined in the living creature, or 

 in some cases — large flies, bees, >fec. — simply dried after the 

 several parts have been opened out by a needle. As speci- 

 mens of tool-provided insects, the student may take a 

 common flea {ptifi'.r irritans), any female gnat, and one of 

 the breeze flies — bluebottle-like flies — common in summer, 

 with splendid green and bronze ej-es, and torments to horses, 

 cattle, and men. JIany other insects might be named, but 

 these will make a good beginning. The head of the 

 creature to be examined should be carefully removed with 

 a needle mounted in a wooden handle. That of the flea is 

 well shown in thin Canada balsam. The others should be 

 mounted entire in couples, one showing the top side, and 

 the other the under side. The flea's head can be best seen as 

 a transparent object in balsam, the others as opaf(ue ones. 

 The flea has to cut through the skin of the animals it feeds 

 upon, and then suck their blood. Very similar is the 

 performance of the breeze fly, but his tools are larger and 

 stronger. The human flea, which differs more or less from 

 some twenty-five other Jleas, has two exquiaitelj'-made saws, 

 with double rows of teeth, a construction used by men 

 wlien they wish to cut green wood, or other clogging 

 substances. They would be reckoned very scientific tools 

 if made by man. The breeze fly, besides his sucking 

 apparatus, has knives like some used in surgical opera- 

 tions ; the female gnat operates with beautifully-shaped 

 lancets, the stings of bees and wasps work in a pro- 

 tecting channel analogous to the tube of the surgeon's 

 trocar. In many insects the tool formation is exhibited at 

 the end of the abdomen as saws and ovipositors, often 

 closely like human inventions. 



In the sponges, the tool-like things are organised mem- 

 branes, infiltrated with the mineral matter. In insects, 

 the strengthening material of the tools is chitin, the sub- 

 stance which forms their external skeleton, and which 

 exists in various degrees of hardness. Its composition is 

 highly complicated, the formula, according to Schmidt, 

 being C,„ IL, N., O,, ; that is, carbon, hydrogen, nitrogen, 

 and oxygen, in those proportions of their several equivalents. 



From the tool-like formations of the sponges, we learn 

 that their life processes are able to arrange matter in 

 shapes that might be called organic inventions, though un- 

 conscious and automatic. If the protoplasm of sponges 

 can do these things, we cannot be surfirised to find the 

 protoplasm of insects directed, at certain points, to similar 

 labours, and, lastly, to find the human brain conceiving 

 forms like those which the organic forces, operating in 

 lower creatures, have produced, and we may wonder whether 

 there is any subtle relation between the two. 



Buyers of microscopes very often — prob.ablj-, most often 

 — get tired of the instrument because though it shows 

 pretty and curious things, they have no train of associations 

 with them. As soon as objects are contemplated in the 

 light of an artistic or scientific conception, their interest 

 is permanent and always on the increase. No attempt 

 has or will be made in these papers merely to describe 

 what popular and accessible books contain, but it is hoped 

 they may excite thinking, and then observation will meet 

 with its reward. 



The ScxnAY Society. — Tho Grosvenor Gallery was open to the 

 members of the Sunday Society on .Sunflay last, each member 

 havinfr the privilepe of introdacinf; a friend. The Gallery was 

 open from six o'clock till half-past eiffht, and during that time 

 720 persons passed tlirongh the turnstiles. Mr. Evans Williams, 

 M.P., Professor Corfield, Mr. Rutherford, and Mr. Mark Judge were 

 present during the evening. 



