152 



HARDWICKE'S SCIENCE- GOSSIP. 



portion as the Quantity increases, till at last they 

 appear entirely black. 



"They were first discovered in a Ditch at Norwich. 

 The length of the Ditch is at least an hundred 

 yards, and its Breadth nine, the Bottom for more 

 than a Eoot in Depth is covered with a blackish 

 green substance in Appearance like Mud, made up 

 wholly of these and other Insects." 



Figr. 81. a, b, Arderon's 

 " Hair-like Insects." 



Fig. 82. Glass jar containing 

 " Hair-like Insect." 



Our "ingenious Friend" Mr. Arderon placed a 

 large spoonful of this dark green matter into a glass 

 jar, which he filled with water, and the next day 

 when he came to examine what had happened 

 ■amongst these " Myriads of little Animals, he found 

 that a Multitude of them had as it were by Agree- 

 ment place themselves on the Side of the Jar, and 

 appeared marching upward in Bows .... A small 

 quantity of this Matter having one day been put 

 into a Jar of Water it so happened that one part 

 thereof went down immediately to the Bottom, 

 whilst the other Part continued floating upon the 

 Top. All Things remained a good while in this 

 condition, until at last each of these Swarms of 

 Animalcules grew weary of its Situation, and had 

 a Mind to change its Quarters. Both Armies in 

 Short began their March at the same time against 

 the side of the Jar, and as one proceeded upwards 

 and the other downwards, after some Hours they 

 were near meeting about Midway .... The De- 

 sire of knowing in what manner they would be- 

 have on this Occasion, engaged the Observer to 

 watch them with a careful Eye, and as they ap- 

 proached still nearer he beheld to his great Surprize 

 the Army that was marching upwards open to the 

 Bight and Left, and leave a convenient Space for 

 the Army that was marching downwards to 

 pass between its Wings. Thus without Confusion 

 or Intermixture each held on its Way." 



The writer proceeds to express his admiration of 

 the sagacity of these creatures, which enabled them 

 to act unanimously for the benefit of the com- 

 munity. 



The reader will probably have been able from 

 the above description to identify this "Hair-like 

 Insect " with what we now know as one of the 

 commonest of the freshwater Algse, Oscillatoria 



nigra or limosa ; the sigmoid form of the filaments, 

 however, does not agree with those of oscillatoria, 

 and we can only suppose that Baker was mistaken 

 in this respect : his friend Arderon says nothing of 

 their shape excepting that they were hair-like, and 

 he had mistaken them at first for the roots of some 

 water-plant. 



Oat Animals. — The identification of this form 

 is by no means so easy as that of the one just de- 

 scribed; it was found in the same ditch-water from 

 Norwich as the preceding, and seems to have been 

 first! detected by Mr. Arderon. The following is 

 Baker's description : — " This Creature is so very 

 small that no true Judgment can be made of it un- 

 less it be looked'at through the greater magnifier, 

 nor even then without considerable attention. I 

 commonly found two or three of them in a 

 Drop of the Sediment amongst Multitudes of the 

 Hair-like Insect lying at the bottom of the water 

 without any visible Motion or Appearance of Life : 

 being enclosed in a Bivalve-shell which the animal 

 can open or shut as it is inclined, but which con- 

 stantly shuts upon being disturbed, nor opens again 

 until after having been quiet for some time. . . . 

 The two ends of the Shell can open whilst the 

 middle Part remains closed, and in that- Condition it 

 is like the Pholas and some Species of the Chama, 

 but differs from them in being able to shut both 

 Ends, and alter the Figure of its Shell, which they 

 cannot do. When these Ends are open the Crea- 

 ture frequently thrusts out at each a cylindrical 

 fleshy Part (fig. 83 c), which may be supposed the 

 Head and Tail, but their minuteness renders it 

 hardly possible to discover any difference between 

 them. In this Posture it is probable the Creature 

 feeds on that Provision the Water brings, though 

 it depends not on such accidence, for it can change 

 its place by Jerks or Leaps, which it makes by the 

 Action of some strong muscles in the two protruded 

 parts whose Spring throws it to the distance at 

 least of its own Shell's Length every time they are 

 exerted. These Leaps, however, have long Intervals 

 between, and. are never made till the Animal is per- 

 fectly undisturbed." 



Fig. 83. " Oat Insects." 



Fig. 81. "The Satyr." 



This is probably some species of Navicula, and 

 the opening and closing of the shell, and the fleshy 

 parts, purely imaginary on the part of the describer, 

 and if this surmise is correct it is probable that 

 this is the first diatom ever detected. 



