MOLLUSCA OF MICHIGAN— WALKER. 455 



water and the cover screwed on, the jar should be left undisturbed for 48 

 hours; it requiring about that length of time to drown the animals. Re- 

 maining undisturbed, they will die fully extended; but, if the jar is dis- 

 turbed in the mean time, more or less contraction will take place. The 

 animal when dead should be thoroughly washed to free it from all adhering 

 mucus, and placed in alcohol diluted with about two-thirds the amount of 

 water, additional alcohol being added from day to day till the mixture con- 

 sists of about 75% of alcohol. The animals should then be removed and 

 placed in undiluted alcohol, the action of the fluid on the integument pre- 

 vents the proper preservation of the internal organs.'' 



^'To remove the shell, preparatory to dissecting the animal, break the 

 peristome with a pair of pliers. The remainder of the shell can be removed 

 with a pair of forceps, carefully breaking off a small piece of shell at a time 

 till it is removed to the apex. The columella can be removed by holding 

 the lower part between the thumb and forefinger of the left hand, and turn- 

 ing the animal ^\dth the right. As the columella is like a screw, the animal 

 readily becomes detached by this movement.'' 



"In dissecting the animal, a circular china dish about four inches in di- 

 ameter and two in depth will be necessary; also a piece of sheet cork as 

 large as will lie at the bottom of the dish, fastened to a thin sheet of lead 

 with either string or rubber bands. It is best to have the lead of the same 

 size as the cork. This leaded cork is to be placed in the bottom of the dish, 

 and the dish filled with alcohol. If the animal has once been placed in 

 alcohol, all dissections should be made in alcohol, but freshly killed speci- 

 mens may be dissected in water, and many of the organs at this time pre- 

 sent a much more natural appearance than when acted on by alcohol. Place 

 the animal on the cork and fasten it down mth small pins, or better yet, 

 wdth very fine, short needles, inserted through the margin of the foot. Then 

 with the fine pair of scissors, commencing at the head, cut through the in- 

 tegument along the center of the back, taking care not to injure any of the 

 organs below. The integument is now to be removed from the dorsal part, 

 turned back and fastened to the cork, removing the needles from the margin 

 of the foot and putting them through the edges of the integument. All the 

 organs of the anterior part of the snail are thus brought into view, and 

 farther dissection of the organs can be intelligently made." 



"In the case of the Limax nearly all the organs will be brought into view 

 by turning back the integument; but great care must be taken in this genus 

 in cutting through the integument not to injure the pulmonary chamber, as 

 it is situated very near the surface. Also every precaution should be taken 

 that the points of the scissors shall not go below the integument, or the in- 

 testine and upper surface of the stomach will be mutilated, and a successful 

 dissection rendered impossible." * 



V. 



PREPARATION OF THE JAW AND RADULA. 



"On opening the head (of the snail) from above, one readily notices at 

 the extreme anterior part, close against the outer integument, a promi- 

 nent, oval body. This is called the buccal mass. It is easily cut away 

 from the animal, and will be found to contain both jaw and Ungual mem- 



* Simpson, Bull. N. Y. State Mussum, VIII., pp. 241-3 (1901). 



