| 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | |
| A. rosea | ······ | —— | —— | —— | —— | —— —— | —— —— | —— ······ | —— | —— | —— | |||||
| A. foetida | ······ | ······ | —— | —— | —— —— | —— —— | —— —— | —— ······ | —— | |||||||
| A. eiseni | ······ | —— | —— | —— | —— | —— | —— | —— | —— | |||||||
| A. caliginosa | ······ | —— | —— | —— | —— —— | —— ······ | —— —— | —— | ······ | |||||||
| A. terrestris | ······ | —— | —— | —— | —— | —— —— | —— —— | —— —— | —— | |||||||
| A. chlorotica | ······ | —— | —— | —— —— | —— | —— —— | —— | —— —— | —— | —— | ||||||
| A. georgii | ······ | —— | —— | —— —— | —— | —— —— | —— | —— |
There are of course other points by which the different species can be distinguished. Colour in a few cases enables a species to be named at once without any further aid. One of the most striking of these cases is the Brandling, so common upon dunghills, and so dear to some anglers. This worm is ringed with brownish purple upon a yellowish ground. The greenish A. chlorotica is often found under stones, and curls itself round into nearly a complete circle when disturbed. A. cyanea, of a bluish grey colour, is one of the earthworms very commonly met with in the early morning in London and the neighbourhood. More generally, however, the colour is of a paler or darker red, verging towards and attaining brown, or even blackish brown; and is so variable that nothing in the way of identification can be attempted from the colour alone, even with the most elaborate description.
Lumbricus, as already mentioned, is distinguished from all Allolobophora except A. eiseni, by the complete dovetailing of the prostomium into the first segment. There are five species in this country which may be thus distinguished by the position of the tubercula pubertatis. The most familiar species is the common L. rubellus.
| L. rubellus Hoff. | tubercula pubertatis are on 28, 29, 30, 31 |
| L. castaneus Sav. | tube"cula pu"ertatis a"e on 28, 29, 30, 31, 32 |
| L. herculeus Sav. | tube"cula pu"ertatis a"e on 28, 29, 30, 31, 32 33, 34, 35, 36 |
| L. papillosus Friend | tube"cula pu"ertatis a"e on 28, 29, 30, 31, 32 33, 34, 35, 36, 37 |
| L. festivus Sav. | tube"cula pu"ertatis a"e on 28, 29, 30, 31, 32 33, 34, 35, 36, 37, 38. |
CHAPTER XIV
HIRUDINEA (LEECHES)
INTRODUCTION—ANATOMY—REPRODUCTION—CLASSIFICATION—RHYNCHOBDELLAE AND GNATHOBDELLAE
"The external appearance of the Hirudinea," remarks Professor Vaillant,[[450]] "permits us, save for rare exceptions, to recognise at once the animals which belong to that group." The leeches are distinguished as a rule by the possession of two suckers, one at each end of the body; their general shape usually differs from that of other Annelids by its oval contour and its dorso-ventral flattening. Cyclicobdella lumbricoides of Grube, which Blanchard has stated to be the same species as Nephelis tergestina, has, however, almost the form of an earthworm by reason of its cylindrical shape and the inconspicuousness of the suckers, while Lumbricobdella also resembles an earthworm and has no posterior sucker at all.[[451]] The Oligochaet family Discodrilidae (see p. [376]) agree with the leeches in their parasitism, in their general shape, in the presence of two suckers, and, furthermore, in the existence of jaws, which are found in no other Oligochaet, but occur in a large number of the Hirudinea. These facts, indeed, though not perhaps important by themselves, are indications of the really close resemblance of the Hirudinea to the Oligochaeta, a group which they approach not merely in such habits as the formation of a cocoon in which the eggs are enclosed, but also in many important points of internal and external structure. Indeed, the fundamental differences between the two groups are not numerous, and are not of such importance as has been given them by some writers.
Leeches are to be found in most parts of the world, in situations which are sufficiently damp for their comfort. But we do not at present possess enough knowledge to state much as to the facts of their distribution. The structure of leeches is not so well known as is that of the earthworms; for they have not been to so great an extent collected in extra-European countries. It would even be desirable to ascertain precisely the species which inhabit these islands, the most recent enumeration (1865) being that contained in the British Museum Catalogue of non-parasitical worms by the late Dr. George Johnston. For Italy this has been lately done by Dr. Blanchard, and a good many of the species are common to the two countries. Johnston enumerates altogether (after subtracting what are probably synonyms) twenty-one species, distributed among the genera Branchellion, Pontobdella, Piscicola, Nephelis, Trocheta, Haemopis, Hirudo, and Glossiphonia (= Clepsine), which number will be possibly still further reduced. The first two genera are marine, the remainder being fresh water or terrestrial; Trocheta has been probably introduced.
