ANNULATA. 227 



8vo. Tab. i. fig. i according to KNOLZ it is this species especially which 

 is used in Vienna and brought there from Hungary 1 . 



Hirudo medicinalis is the most useful species of Leech (sangsue, leech, 

 Blutegel), which almost everywhere in Europe lives in fresh water, especially 

 in ponds, marshes and canals, and in winter, rolled up annularly, conceals 

 itself in the mud. This animal lives on the blood of animals (vertebrate and 

 invertebrate) exclusively; the jaws serve to wound and to penetrate the skin. 

 The first segment of the body, which also is occasionally parted by a trans- 

 verse stripe, has a semilunar form and is not closed beneath. It can extend 

 itself as an upper lip for feeling or bend itself downwards to cover the 

 mouth. The ten black eye-spots are arranged in form of a horse-shoe on 

 the back-side of the head ; the first on the first segment, the two next on 

 the third, and the two last on the sixth ring of the body. The organs of 

 propagation of the leech are by different writers determined very differently, 

 whilst, however, the latest investigations (especially of H. MECKEL, 

 MUELLER'S Archiv. 1844, s. 476 480) bring us back to the generally 

 received opinion of former times. According to it, nine pairs of round 

 vesicles of a white colour are testes, (TREVIRANUS thought they must be 

 held to be ovaries, Zeitschr. fur Physiol. iv. 2, 1832, s. 159 167). By 

 means of short transverse tubules these vesicles are connected with a com- 

 mon canal which runs at each side of the body ; this canal goes forward 

 into a structure which is white and consists of many convolutions (the 

 epididymis or the seminal vesicle). From each of these two seminal 

 vesicles arises a, short vessel (vas ejaculatorium), which runs to the spherically 

 widened sheath of the penis : the penis can be everted outwards through 

 an opening in the twenty-fourth ring of the body. In the fifth ring 

 behind this is seen the second sexual opening, that of the female parts ; it 

 leads to a wide vagina (uterus, according to BOJANUS) which, by means of 

 a tube that divides forwards into two branches, is connected with two 

 small ovaries or vesicles filled with granular bodies. These two ovaries lie 

 between the seminal vesicles and the vagina. The impregnation in Leeches 

 is mutual. The Leech lays eggs, or rather capsules, in which eggs 

 are contained, 5 16 in number. These capsules or cocoons are three- 

 fourths of an inch long, oval and surrounded with a spongy or frothy 

 substance, and filled with a brown albuminous fluid. The germs appear as 

 round discs ; these minute yelks grow by means of the surrounding 

 albumen, which is absorbed by a structure which closely resembles a funnel- 

 shaped oesophagus, and is already visible on the germ when only half a line 

 in size (E. H. WEBER in MECKEL'S Archiv. 1828, s. 366 418, MUELLER'S 

 Archiv. 1846, 8.428 434). 



Comp. on the Leech amongst others : JOHNSON, Treatise on the Medicinal 

 Leech, London, 1816, 8vo, and by the same, Further Observat. on the Med. 

 Leech. With engravings. London, 1825, 8vo ; KUNTZMANN, Anatomische 

 Physiol. Untersuchungen ilber den Blutegel, m. 5 Kupfert. ; BOJANUS in 



1 Other species still, which have been discovered, may be used for drawing blood, 

 \ the large black species spotted with white which was discovered in Sweden some 

 jars ago by WAHLBEEG, and named Hirudo albopunctata. 



152 



