272 



KNOWLEDGE 



[December 2, 1895. 



ments were capable of living in the water examined under 

 the same conditions of temperature, Sec, that the test is 

 performed under. 



Besides the filters having a candle form, there are a few 

 existing at the present time which are successful in 

 reducing the number of microorganisms present in a water, 

 although not able to produce absolute sterility. Thus, for 

 example, certain filters are now being introduced which 

 have for their filtering area a disc of natural stone, which 

 it is believed has the power of arresting a large percentage 

 of the micro-organisms naturally occurring in water. 

 Thfse discs must, however, vary in efficiency with the 

 nature of the stone, and also the thickness employed, and 

 so far as I am aware no accurate experiments in this 

 direction have been published. 



Under the name of "nibestos" another similar filtering 

 medium has been designed, which consists of asbestos pulp 

 pressed into thin sheets, or filtering discs, which are 

 supported upon an earthenware or glass plate containing a 

 number of holes. Such a filter acts like a Gooch crucible, 

 frequently used in analytical operations, and which, if 

 properly made, retains even the finest precipitate. Its 

 behaviour towards micro-organisms has not been sufficiently 

 demonstrated since Dr. Sims Woodhead and Cartwright 

 Wood's experiments showed that the filtrate was not 

 sterile, although the number of organisms were diminished ; 

 whereas Prof. Attfield, in earlier experiments, obtained 

 sterility. At the present time the nibestos films are being 

 made much thicker, so presumably they give better results, 

 but there has not been published any direct evidence upon 

 this point. It is certain, however, that they cannot be 

 considered germ-proof in the same sense as that term is 

 used in connection with the Pasteur and Berkefeld filters. 

 It is impossible in the present article to discuss the alter- 

 nate method of sterilizing water, viz., by the action of heat. 

 It may be that eventually all filters will be discarded in favour 

 of heat sterilization. I have already endeavoured to show 

 that, with the exception of only a very few types of filters, 

 their use is worse than useless, as they rendered the water 

 liable to an increased instead of to a diminished contami- 

 nation. The boiling of water and milk is always a ready 

 and efficacious method for destroying germs, and unless a 

 filter can be constructed which will continue to give sterile 

 water without much attention, the boiling of the daily drink- 

 ing water has a good deal to be said in its favour. Apart 

 from this easy method for ensuring freedom from water- 

 borne disease, within recent years several methods of 

 sterilizing water by heat on a large scale have been brought 

 to perfection. These sterilizers, as they are called, are 

 gradually finding their way into hospitals and dispensaries, 

 as well as into private houses and for technical purposes, 

 owing to the fact that their simplicity of construction and 

 reliability more than compensate for the cost of fuel 

 required for working them. 



WHIP-SCORPIONS AND THEIR WAYS. 



By E. I. PococK. 



ALTHOUGH, as their name implies, the whip- 

 scorpions offer a strong superficial resemblance 

 to the true scorpions, they are in reality more 

 nearly alHed to the spiders. The most obvious 

 points of likeness between them and the scorpions 

 lie in the fact that the appendages of the second pair have 

 lost their leg-like appearance, and have been transformed 

 into powerful prehensile organs or pincers, and that the 

 abdomen is composed of a series of distinct segments, the 

 posterior of which are narrowed to form a stalk, bearing a 



! many-jointed thread-like tail, which undoubtedly corre- 

 sponds morphologically to the scorpion's poison-sting. But 

 to all intents and purposes the resemblance ceases here ; 

 for if we refer to the embryological history and to other 

 structural details, we find striking features of similarity 

 between the whip-scorpions and the spiders. In both, for 

 instance, there is a narrow waist separating the thorax 

 and abdomen, and in both the abdomen is provided with 

 but two pairs of breathing sacs, whereas in the scorpions 

 there are ioxxr pairs of these organs ; and in neither is 

 there a trace of those curious abdominal appendages, the 

 combs, which are so characteristic of scorpions. So, too, 

 j in the structure of the nervous and circulatory systems, is 

 j the relationship between the whip-scorpions and spiders still 

 further established. Nevertheless, the special characters 

 of the former are sufficiently well marked to allow of their 

 being separated as a distinct order from the spiders or 

 Aranese. This fact was long ago recognized by Latreille, 

 who proposed to include the whip-scorpions or Thcli/jiJionida 

 and the Phrt/niihp in his order Pedipaliii. The name " pedi- 

 I palpi " or palp-footed was ascribed to these families of 

 I Arachnida in allusion to the peculiar formation of the first 

 i pair of legs. A glance at the accompanying figure of 

 I Hose's whip-scorpion (TheJyphon'us hosci), from Sarawak, 

 will show that the appendages in question are much longer 

 and thinner than the rest of the legs, and that the tarsus 

 is divided up into a series of small segments and is claw- 

 less. These limbs, in fact, are never used for locomotion, 

 for which indeed they are quite unfitted, but take the 

 functional place of the antennse of an insect, and enable 

 their possessor to learn by touch the nature of the sur- 

 roundings in which it is placed. There is no doubt that 

 this end is also partially attained in the case of Theh/phoniis, 

 by the long, pliable, whip-like tail, which is thickly studded 

 with tactile hairs. In the Phrynidae or tailless Pedipalps, 

 on the other hand, in which this posterior feeler has dis- 

 appeared, we find the want of it made good by the exces- 

 sive development of the anterior feelers, which are some- 

 times as much as eight times the length of the animal's 

 body, the three distal segments of the limb being trans- 

 formed into a long, many-jointed antenniform lash, which 

 can be projected with equal ease forwards, backwards, or 

 sideways, the two together covering in large specimens an 

 area upwards of twenty-four inches in diameter. 



The whip-scorpions have no poison glands for killing 

 prey, such as are possessed by spiders and scorpions, but 

 they speedily slay insects with the deadly embrace of 

 their pincers, which are armed for the purpose with stout, 

 horny spines. 



The adult males are very different from the females in 

 appearance, being smaller and thinner in the body and 

 having the pincers much longer and stouter. The reason, 

 however, of these structural differences in the pincers is 

 not yet understood. 



The geographical distribution of these animals is both 

 interesting and puzzling. They range in south-eastern 

 Asia from Japan and the Kiver Amur in the north to South 

 India and Ceylon in the south. Thence in an easterly 

 direction they spread throughout the islands of the Indo- 

 and Austro- Malayan Archipelagos, including the Philip- 

 pines, as far as the Fijis and the New Hebrides, perhaps 

 just touching the north of Queensland on the way. But 

 from the greater part of Asia, the whole of Europe, of 

 Africa, including Madagascar, of Australia, with the above- 

 mentioned exception, and of New Zealand, they are, so far 

 is at present known, entirely absent. In America their 

 distribution closely resembles that of scorpions and other 

 tropical and sub-tropical groups, for they extend from the 

 Southern States (Texas, Florida, etc.), through Mexico 



