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Art. VI. — A few notes on two kinds of Australian Leeches. 

 By Ltjdwig Becker, Esq. 



[With a Plate.*] 

 [Bead before the Institute, 28th July, 1858.] 



While I was engaged in drawing Australian Leeches of two 

 kinds, for the illustration of Mr. J. Bosisto's descriptive paper, 

 I made a few observations whk- I think, will be found not 

 quite valueless for distinguishing the true Australian medici- 

 nal leech from others. 



Fig. 1 represents the back of the hirudo medicinalis of 

 Australia ; three black lines are running longitudinally over 

 the middle part of the back, and one black line along each 

 side. The ground-color of the upper half of the body is a 

 yellowish brown, while the under side (Fig. 2) is of a deeper, 

 more rusty, hue. On some specimens, small black lines are 

 seen across the belly, as in Fig. 3 ; but these are accidental 

 and do not indicate a different species. The body of the true 

 Australian medicinal leech is divided into 97 rings, and each 

 ring is again very regularly divided by transverse folds (vide 

 Fig. 5, showing part of the under side magnified) . It is pro- 

 vided with four pairs of eyes, placed near the end of the head, 

 as seen in Fig. 4 (magnified). The skin upon the inferior 

 surface of the body has eighteen pairs of pores, exuding a 

 mucous secretion ; four rings are between each pair of these 

 pores (Fig. 5) . The cocoon (Fig. 7, nat. size) is covered with 

 a sponge -like tissue, of an olive-green color (Fig. 6, nat. size) . 

 Part of this tissue is magnified in Fig. 8. The cells, or meshes, 

 of this tissue appear to be formed by flattened threads of a 

 skin-like membrane, joined together in such a manner as to 

 produce cells or meshes of different angular forms. That part 

 of the sponge-like tissue which is nearest to the cocoon, has its 

 meshes closed by a layer of skin, serving as the epidermis 

 of the cocoon. Fig. 9 shows part of the epidermis, magni- 

 fied. The cocoon is filled with a dark brown fluid, which is 

 visible through the semi-transparent inner skin forming the 



* Since the completion of this Plate, it appears, after the examination 

 of various specimens, that the following emendation is necessaiy. Fig. 10, 

 besides the central line of a jet black color, there exists three faint brown 

 parallel lines on either side.— [Ed.] 



