Ill 



AN SKI. lli.V. 



ANNKI.IPA. 



1 inch by 4 an inch broad, and a | inch thick ), of cinders, and a few quartz 

 pebble* mingled with earth ; lastly, about 4 J inches beneath the surface 

 WM the original black peaty toil Thus beneath a layer (nearly 

 4 inchei thick) of fine particle* of earth, mixed with some vegetable 

 matter, thoM nbrtanoe* now occurred, which, 15 yean before, had 

 been spread on the surface. Mr. Darwin lUled that the appearance in 

 all owes WM ai if the fragment! had, as the farmers believe, worked 

 themselves down. It doei not however appear at all possible that 

 either the powdered lime or the fragment* of Limit marl ami the 

 pebbles could gink through compact earth to some inches beneath the 

 surface, and still remain in a continuous layer; nor is it probable that 

 the decay of the gnus, although adding to the surface some of the 

 constituent parts of the mould, should separate in so short a time the 

 fine from the coarse earth, and accumulate the former on those objects 

 which so lately were strewed on the surface, Mr. Darwin also remarked 

 that near towns, in fields which did not appear to have been ploughed, 

 he had often been surprised by finding pieces of pottery anil l>ncs 

 some inches below the turf. On the mountains of Chile he had been 

 perplexed by noticing marine shells, covered by earth, in situations 

 where rain could not have washed it on them. 



The explanation of thego circumstanced, which occurred to Mr. 

 Wedgwood, although it may at first appear trivial, the author does 

 not doubt is the correct one, namely, that tin- whole is due to the 

 digestive process by which the Common Karth-Worm is supported. 

 On carefully examining between the blades of grass in the fields 

 above described, the author found that there was scarcely a space of 

 two inches square without a little heap of the cylindrical castings of 

 worms. It is well known that worms swallow earthy matter, and 

 that, having separated the serviceable portion, they eject at the mouth 

 of their burrows the remainder in little intestine-shaped heaps. The 

 worm is unable to swallow coarse particles; and as it would naturally 

 avoid pure lime, the fine earth lying beneath either the cinders and 

 burnt marl, or the powdered lime, would, by a slow process, be 

 1 and thrown up to the surface. This suppoition is not 

 imaginary, for in the field in which cinders had been spread out only 

 half a year before, Mr. Darwin actually saw the castings of the worms 

 heaped on the smaller fragments. Nor is the agency so trivial as it 

 at first might be thought, the great number of Earth-Worms (as every 

 one must be aware who has ever dug in a grass-field) making up for 

 the insignificant quantity of work which each performs. 



On the above hypothesis, the great advantage of old pasture-land, 

 which farmers are always particularly unwilling to break up, is 

 explained ; for the worms must require a considerable length of time 

 to prepare a thick stratum of mould, by thoroughly mingling the 

 original constituent parts of the soil, as well as the manures added by 

 man. In the peaty field, in 15 years, about 34 inches had been well 

 digested. It is probable however that the process is continued, 

 though at a slow rate, to a much greater depth ; for as often as a 

 worm is compelled by dry weather or any other cause toil 

 il -ep. it must bring to the surface, when it empties the contents of it 

 bo ly. a few- particles of earth. The author concluded by remarking, 

 that it is probable that every particle of earth in old pasture-land has 

 passed through the intestines of worms, and hence that in some 

 sense* the term 'animal mould' would be more appropriate than 

 ' vegetable mould.' The agriculturist, in ploughing the ground, 

 follows a method strictly natural ; and he only imitate* in a rude 

 manner, without being able either to bury pebbles or to sift the tim- 

 fnim the coarse soil, the work which Nature is daily performing by the 

 agency of the Earth- Worm. 



The most common species of Armieola is the A. Pueat-orum, or 

 Lug-Worm, which is commonly employed on the coasts of this 

 country as a bait by fishermen. 



The gemm AViu, of Linnaeus, includes a number of small Annelides, 

 not well made out. They live in holes which they perforate in the 

 mini at the bottom of the water, from which they protrude the upper 

 i of their body, which they are incessantly moving. 



The Sttftoria are" characterised by the body of the animal* being 

 destitute of bristles for locomotion, completely apodous, without soft 

 appendages, and furnished with a prehensile cavity in the form of a 

 sucker at each extremity. The head is not distinct, but generally 

 pniviiled with eyes and jaws. 



Tin 1 principal family of thi* order in the /firinliniilir. which comprc- 

 not only the Leeche* properly so called, which live by sucking 

 ill- I.I.....I nf various animals, hut also includes many otln -r worm* 

 which derive their nourishment in a totally different way, and present 

 corresponding difbrenees in organisation. The affinities between the 

 leeches and some of the Sutiienm- Annclidans, a* various p> 

 tfrrrii, Lumbrictu, Ptanaria, ftc., are so dose that they him I! v admit of 



being arranged in separate orders, and other* of tin- I. h tribe may 



even be confounded with ome species of Lrrnttt or Ki>i:nn. 



The ancient* appear to have only known the most common species 

 of Leeches. Aristotle make* nn mention .,f them, mul they do not 

 appear to have been used in nn-li im- in the time of Hippocrates, 

 i'liny describes them very clearly under the nan. net and 



Sangi*mffte, and distinguishes two species. Tin- Se :i Leech i* dis- 

 tinctly mentioned by Baton, lion. 1, 'let. and by all the wr 

 natural history since the revival of let " i recently I.. 



increased our knowledge of the number of species, of which he describes 



eight in the 12th edition of th wards 



discovered five or so that Gmelin. in hi* i 



'Systems Natur.i-,' enumerated fourteen ipeoiei. Since then, Shaw, 



Leach, I'uti ny, Milne-Edwards, and others, have found 



many more, and the intr 



a necessity for arranging these various species in dilii-rent gen 



which we shall enumerate some of those which are best known. 



The True Leeches are all destitute of branchiae or special organ* f 

 respiration ; and thi* function has been supposed to be effected by 

 means of the skin generally, but M. Miluc Kdward* ha* r. 

 stated (as was before observed by Cuvier) that " there exists in these 

 Annrlitltt a series of small membranous sacs, each of which commu- 

 nicates externally by a minute orifice situated on the ventral aspect 

 of the body : these sacs derive from the numerous vessels which 

 minify upon their parietes a considerable quantity of blood ; 

 penetrates into thme organs, and seems to subserve a true respiratory 

 purpose." But though the species of the family // 

 provided with distinct branchieo, these organs are fonml in a genus 

 which is generally associated with the True Leeches, and win 

 shall place first m the following list of g, i 



1. Hranrkrlliim, Savigny, Branckiobddla, IV P.lainvill. 

 Oken. These names have been given to a worm closely resembling 

 a leech in external structure (it being fnrnixhcd with i , 

 which is found parasitic on the Torpedo in the Mediterrane.v 

 other seas. The /.' i-liin'n, Men/ie*, a species observ 



the tortoise which is found in the Pacific Ocean, has also been ] 

 in this genus, though Cuvier says that it ought not to be associated 

 with it. 



// ',,.. 7,r proper. 



Section L Anterior -^ 'sated from Hit Body by a di 



f 



2. Albione, Sav., PomtoMeUa, Leirh and Hlain., characterised by 

 the body being bristled over with tubercles. Species all marine : 



have been enumerated; two of them are very common 

 seas: 1, Albione verrueota, II <>/'>;. l.inmcu*; 'J. , 



Mclla tpinulom, Leach : both of these worms attach themselves to fish, 

 particularly skates; and the latter species is commonly known to 

 fishermen by the name of the Skate-Sucker. 



.'!. Hiemocharit, Sav. ; /</i'/<yobdeUa,]3\a,h\. In this genus there are 

 eight eyes, the body is narrow, and the jaws scarcely \i.-iblc. The 

 only known species i the //(emoc/tari* Pucitun, J/irudo Purium, I. inn., 

 which lives in fresh waters, where it attached itself to fish, particularly 



Section II. Anterior Sucker reri/ tl!yhtly sriiaratrd from the Body. 

 '4. Geobdella, Blain., Trochetia, Dutrochet, is distinguished by having 

 an enlargement round the orifice* of the genital organ*. We only 

 know one small species of this genus, the (itobiiella Trochrtil, which 

 inhabit*) our which frequently comes on land to pursue the 



'/, or Karth V> . 



5. Pteudobdella, Blain., has the mouth merely provided with fold* 

 of skin, and is destitute of teeth. Only one species is well known, the 

 Pteudobdella niV/nr, //<'/</ nl;/ra. Linn., the Common Black Leech. 



i!. /{, i mi>/ii*, Sav.. Jliijutlnlillii. Blain., has the mouth furnished with 

 a few obtuse teeth. Three species are enumerated; the l.ot known 

 istheflmnopitfanguisorlxi. Sav.. //</</... -111111011 



Horse-Leech, which is much larger than the Medicinal I.eeeh. and w holly 

 of a greenish-black colour. The Horse-Leech ho* been reported to indict 

 dangerous wounds by some o 1 ! ule other- never 



attacks vertebrate animals. M. De Blaiuvillc thinks that thi* ,li-, r. 

 pancy has ari*en front thi* species having Ipcen confounded with the 

 foregoing, the Black Leech, which cannot p. vbrate 



animals for want of teeth. Both these leeches greedily attack the 

 common earth-worm. 



7. 8a -viv., Jatroodflla, Blain. The anterior sucker has its 



upper lip divided .1 segments. Its aperture is transverse, 



and it contains three jaws, each of which is armed on its edge with 

 two ranges < -eth. which enable these leeches to penetrate 



through the skin without making any dangerous wound. Thi- 

 contains the true Medicinal Leeches, eight specie- of which ha\. 

 enumerated: the mo-t common i> the >.I./HI.< 

 in- tl n-iiialii. Linn., which is a native of all our stagmuit. fiv*h waters. 



\ /.-/ ^./. s t ; .. h:i - , iL, r ht c\ e* and is d< teeth: one species 



i, found in t!i. 



9. A'iy/"/' -1,11,11:1. Klain., has eight eyes, and the month 

 is furnished .internally with only three fold* of skin. Several - 



of this genus are enumerated ; the most common is the jVi;i//i' 

 //"' ';>/.<, I. inn. This specie* lias often. been 



confounded with the nic'iicinal and oilier leeches ; it i* coninionly 

 found in fiv-h water-, and, like all the other species of this genus, m >< -r 

 injured by the contact of the air; no that if 

 taken out of the water it quickly dies. 



Section III. Anterior Sucl-'r vaniiuy. 



10. I' <v., t;i,Hum]>ora, Johnson, (;/ttot><l<lln, lilnin. This 

 genus has a widen d Imdy and "ill. r flicker; tin' mouth is 

 in the form of .1 proboscis. Cuvicr think* it doubtful whether the 

 species of this genus should be arranged with the Lc> 



