470 ZOOLOGY. 



The most satisfactory way to get rid of it is to bathe the 

 hands in a solution of permanganate ("Condy's fluid"), 

 diluted to a light pink colour, and afterwards with soap 

 and water. 



Formalin-preserved dogfish are much less objectionable 

 than others. 



AmpMoxus affords good practice for those who enjoy fine 

 dissection, but is distinctly difficult for the ordinary student. 

 We advise the following as the best procedure : Use as shal- 

 low a dissecting-dish as possible, and work in a good light. 

 Best your wrists on some solid support while dissecting 

 (this advice applies to all fine work). Holding the lance- 

 let in one hand insert the point of a fine pair of scissors 

 into the atrial pore, and cut forward along the middle line 

 of the floor of the atrium, taking great care not to push 

 the point of the scissors farther into the cavity than is 

 absolutely necessary, or you may cut open the pharynx 

 also. Stop cutting just short of the mouth-region. Then 

 lay hold of both cut edges simultaneously by means of 

 two pairs of forceps, and gently draw them apart, until 

 you can clearly see both pharynx and liver, and that they 

 are both separated from the atrial wall. If this is not 

 done the liver at least is sure to adhere to the atrial wall, 

 and will be badly damaged in the subsequent dissection. 

 You can now r pin the animal down on its left side (dissect 

 from the right side in order to display the liver). Three 

 pins (the smallest size obtainable) will be enough to 

 transfix it: two through the notochord (whose position is 

 marked on the surface by the V-shaped bend in the 

 myomeres) and the other through the left atrial wall. 

 The right atrial wall, with the right gonads, may now be 

 cut away with scissors, and then the rest of the muscles 

 of the body gradually dissected away. It is advisable, 

 while this is being done to turn the dissection round so 

 that the dorsal side is towards you; you are then less 

 likely to injure the pharynx. In this way all the essential 

 structures can be exposed in a single side dissection. If 

 the dissection is properly done, the sphincter oris muscle in 

 the velum will be plainly visible just behind the prse- 

 oral cirri and their supporting hoop : the two may be 

 removed together. The sphincter with its tentacles if the 



