MOLLUSC A. 153 



interesting objects for the microscope, the structure of the 

 viscera, the spermatozoa, and the tongue or odontophore 

 being the chief. Fresh-water and land snails should be 

 avoided by the student until he has gained sufficient 

 experience in the manipulation of limpets and whelks, from 

 which the extraction of the odontophore is a comparatively 

 easy operation. The marine molluscs may be carried long 

 distances folded in damp sea-weed, while fresh-water snails 

 should be conveyed in a similar manner in damp Anacharis. 

 When the animals are not immediately required, they may 

 be dropped into glycerine, dilute acetic acid, or into alcohol. 

 Edwards advises that they be dropped into caustic potash 

 solution (say one part of caustic potash and two of water), 

 until they begin to decompose ; but of course this is only 

 admissible when nothing but the odontophore is required. 



This odontophore is the so-called tongue or lingual 

 ribbon, really the masticatory apparatus, a long ribbon-like 

 organ furnished with a com- 

 plicated system of teeth, gene- 

 rally set upon flattened plates. 

 The form and arrangement of 

 the teeth furnish characters 

 of much importance in classi- 

 fication, and therefore should 

 be studied by all those who 

 are interested in this depart- F IG . I4I . 



ment of natural history. 



Fig. 141 shows a short length of the odontophore of the 

 common limpet, Patella vulgata. 



Books which may be consulted. ' British Mollusca/ 

 Forbes and Hanley ; " Notes on Victorian Molluscs and 

 their Palates," C. M. Mapleston, 'Monthly Microscopical 

 Journal/ vol. viii. p. 45 ; Alcock, ' Proceedings of Man- 

 chester Literary and Philosophical Society.' 



