Author's Note on the Use of this Memoir as a 

 Guide to Dissection. 



As the L.M.B.C. Memoirs are read mainly in Universities, it is 

 thought advisable to indicate how this Memoir may be used to 

 advantage by the students of a general zoological course. This is 

 the more necessary since a few of these Memoirs have become 

 original treatises and contain a considerable amount of detail which 

 may be passed over by the ordinary student. In a practical course, 

 such as that for the Final B.Sc. examination, where the following 

 molluscan types are examined : — Chiton, Patella, Buccinum, Helix, 

 Doris, Aplysia, Pecten, Anodon or Mya, and a Cephalopod — 

 Buccinum would be used to contrast with Patella and with Helix 

 as the type of a marine Prosobranch. 



Whelks narcotised in sea-water containing cocaine should be 

 used for dissecting. The shell should be removed at once by 

 breaking away with bone forceps. The animals should then be 

 preserved in 5 per cent, formalin ; some should also be preserved in 

 alcohol for dissection of the nervous system. The vascular system 

 should not be neglected. Injections are easily carried out if the 

 whelks are obtained alive and narcotised in the laboratory. The 

 pages of the Memoir that are of most importance to the student 

 should then be taken in the following order : — 



I. General organisation and shell p. 3-7 



Foot and operculum, p. 10-15 



II. Cut open the pallial cavity by a slit down the right side close 

 to the rectum. 



Pallial cavity p. 17-19 Mucous gland p. 26-28 



Respiratory organ p. 21-22 Osphradium p. 77-78 



III. Examine gonads from exterior p. 89-93 



IV. Cut into renal organ along right side p. 83-88 



V. Dissect alimentary canal, removing proboscis p. 28-35 



VI. Dissect proboscis p. 43-50 



VII. Dissect nervous system p. 65-73 



VIII. Blood system on injected animal p. 56-65 



Microscopic Work. — Confining the histology to a few of the 

 more special points that can be studied to advantage in the whelk, 

 the following permanent preparations should be made : — 



Eye p. 73-76 Radular sac p. 52-54 



Osphradium p. 77-82 Cartilage of tongue, p. 51 



Radular muscles, p. 50 Gill p. 22-26 



QL 1*8 



