October 1, I'JOO.] 



KNOWLEDGE. 



221 



of liquid could be detected entering and leaving the 

 abdomen, as iu the other chief group of the Odonata, 

 was found to be stained with the pigment iu the five last 

 segments of the abdomen, the other segments, together 

 with the head and legs remaining green, as before, 

 but the proof that the pigment was drawn in by respira- 

 tion through the skin was not by any means conclusive. 



The other chief group of the Odonata perform the 

 act of respiration iu a different manner. The abdomen 

 terminates in five more or less pointed appendages, two 

 of them short and three longer. 



In J-Jsclina cyanea. a member of the Anisoptend group, 

 two of these latter appendages are sharp spines, and arc 

 used as weapons of offence ; the third, which is called the 

 upper anal appendage, is somewhat obliquely truncated, 

 axid all three are grooved within, forming a minute 

 chalinel when closed together. The effect of the upper 

 anal appendage being truncated is that this channel, 

 fine as a small bristle, is always open to the element 

 the nymph is in, whether air, or water, even when the 

 spines ai^e quite closed. 



Ordinarily these spines are kept wide open, and water 

 is admitted to the interior of the abdomen and expelled 

 therefrom by the regular dilation and contraction of 

 the ventral side of the abdomen, the dissolved air being 

 abstracted b\' certain folds in the last part of the in- 

 testine and distributed thence through the tracheal 

 system. 



The rate of breathing, which is very easily observed, 

 varies from about thirty pulsations a minute to twenty, 

 seventeen, or even thirteen a minute, the nymph at 

 times remaining for several minutes at a time with all 

 the anal spines closed, ajid without any perceptible 

 dilation or conti-action of the abdomen. 



Now the fact of this anal channel alwaj-s remaining 

 open, even when the spines terminating the abdomen 

 are closed tightly together, is connected with a very 

 extraordinary faculty possessed by one at least, and 

 possibly all, of the members of this group of the 

 Odonata. 



Of more than two hundred individual nymphs of 

 ^schna cyanea observed, every one spent about the last 

 two weeks of its aquatic life (minus the final two r)\- 

 three days) wi^h the tip of the abdomen clear of the 

 water, and the anal passage open to the air ; when 

 disturbed the nymphs would descend a short distance 

 down the stick they rested on into the water, and return 

 very shortly to their former position. During the two 

 or three days immediately preceding emergence the 

 position was reversed, and the head and thorax were 

 protruded into the air as far as two large breathing 

 apertures on the fore part of the body, called the 

 thoracic spiracles. These .spiracles under a lense could 

 be seen to be open and they are connected with well 

 developed tracheEe. This habit suggests very strongly 

 that during the last fortnight of its aquatic life the 

 nymph breathes the outer air direct into the tracheal 

 system. 



Being anxious to know whether this faculty is confined 

 to the later nymph stages alone, the writer lately pro- 

 cured some nymphs of JS. cyanea, about 1^ inch long, 

 and kept them out of water in damp weed, and the 

 result is not a little surprising. Two nymphs have 

 been living out of water for more than two months with 

 only " short intervals for refreshment," and are as well 

 and vigorous when put back into water as when first 

 removed from it, and take their food with the wonted 

 appetite of their kind; the intervals between visits lo 



the water have varied from two days to twenty-eight 

 days, and the times in the water have varied from two 

 minutes to twenty hours; during its aerial periods 

 the nymph is perfectly quiescent on the weed, and re- 

 sumes its aquatic life exactly where it left off. Nor 

 does this extnvordiuary faculty of living in both elements 

 alternately seem confined to nymphs of which Ji. cyanea 

 is an example. 



Four nymphs of the Zygopterid group, viz., Agrinn 

 puella, have lived under similar conditions for thirty- 

 three da3's without visiting the water at all, and appear 

 perfectly vigorous and healthy. Similarly Erytlinnniiia 

 Xaias lived from March 16 to April 16 in damp weed 

 only. 



The present writer was led to investigate by the 

 accident of leaving one nymiWi for some days in an 

 empty bottle by mistake, and finding it well and hearty 

 at the end of that time. It is time that this observation 

 was only made on three species, but they arc repre- 

 sentative of both the Anisopterid and Zygopterid 

 groups, and there is no structural i-eason why the same 

 faculty should not be possessed by all the Odonata 

 nymphs in an equal degree. 



This faculty seems to be closely akin to that of the 

 common crayfish of our streams, of which Huxley, in his 

 '' Introduction to Zoology," writes : " As is tlie case with 

 many fishes, the crayfish breathes very well out of the 

 water if kept in a situation sufficiently cool and moist 

 to iDrevont the gills from drying up, and thus there is 

 no reason why, iu cool and damp weather, the crayfish 

 should not be able to live very well on land, at any 

 rate amongst moist herbage." 



Consequently, the explanation that the nymphs 

 breathe through the skin may, perhaps, be dispensed 

 with, when the nymph is out of water, and true aerial 

 breathing substituted. One's only regret is that thus 

 the point would seem to be removed from one of Mrs. 

 A. Gatty's most beautiful " Parables from Nature." 



THE EVOLUTION OF SIMPLE SOCIETIES. 



By Professor Alfred C. Haddon, m.a., sc.d., f.r.s. 

 v.— THE METAMORPHOSIS OF HERDERS INTO 



TILLERS. 

 Ix the article on " The Beginning of Agriculture " it 

 was stated that a powerful constraint is necessary to 

 force pastoral communities into the uncongenial occupa- 

 tion of agriculture. Again closely following M. Demolins 

 I shall briefly describe how this constraint has been 

 exercised upon two very different groups of herders. My 

 French colleague has in his turn drawn upon the obser- 

 vations made on the spot by Le Play, and published in 

 his " Ouvriers Europeens," Vol. II., chaps. 1 and 8. 



EsviR0NME.\T. — The first locality selected for study is 

 the village of Mochmet, which is situated on the ca.stcrn 

 slopes of the Ural Mountains between Troitzk and 

 Ekaterineburg, close to the great divide on the upper 

 portion of the valley of Miask. Thus this village is 

 located on the last of the Siberian slopes, and conversely 

 is at the first point of contact with the sedentary popu- 

 lations of Europe. It is inhabited mainly by Bashkirs, 

 who fomierly were nomadic pastors, as their brethren 

 still are on the neighbouring steppes, 



Two conditions are necessary to enable a people to 

 pass from a pastoral mode of life to cultivation of the 

 soil: — 1. The soil must naturally or artificially receive 

 a sufficiently prolonged irrigation. As we have seen, 

 owing to the short season of humidity, grass, jJractically 



