48 A Guide to the Zoological Collections in the 



of an alimentary canal, and leading therefore only a tran- 

 sient life. 



An enlarged diagrammatic drawing of a female Rotifer, 

 in side view, is exhibited in Case 44- 



3. ANNELIDA HiRUDINEA- 



[® est cm SEaU-rasc 44]. 



The third class of the Annelida includes the Hirndinea 

 or Leeches. 



Ihe Leeches, like the Earth-worms, have a ringed and 

 segmented body; the rings however are only external 

 markings and must not be confounded with the " segments", 

 for each segment consist of five rings. The segments of 

 the Leeches differ from those of the other Annelids in being 

 destitute of appendages (parapodia and setae) of any kind. 

 Locomotion is effected entirely by suckers, of which there 

 are usually two, one at the fore end and one at the after 

 end of the body. In the anterior sucker lies the mouth, 

 which in some leeches is provided with three jaws disposed 

 in Y-fashion and each armed with a saw-like series of 

 chitinous teeth. 



The nature of the internal organization of the Leeches 

 is shown in the spirit dissections of the large Horse leech, 

 in Case 44, alongside of which is an explanatory drawing. 

 Of the Leeches a few are marine, but the greater number 

 live either in freshwater or in damp places on land. The 

 marine Leeches are represented in the collection by fine 

 specimens of Pontohdella from the European seas. The 

 terrestrial leeches are represented by the following genera 

 from India : — Hirudo, Hsemodipsa^ and Lininatis. 



The habits of the leech are proverbial. 



APPENDIX TO THE PHYLUM 

 ANNELIDA. 



As an appendix to the Annelida we may here consider 

 the Gephyrea, the Brachiopoda, and the Polyzoa^ three 



