378 PRESERVATION OF MARINE ORGANISMS 



instead of formalin-spirit. For their further treat- 

 ment, see p. 359. 



We are indebted to Mr. R. T. Leiper for the follow- 

 ing notes on the preservation of parasitic worms. 



(a) Preservation. 



Nematoda. — The worms are washed by shaking in 1 per cent, 

 saline solution, killed by plunging each separately into a 

 quantity of 70 per cent, alcohol that has been heated to its 

 boiling-point, and stored in fresh 70 per cent, alcohol for 

 examination. If this method is properly applied the worms 

 should die in an extended and straightened position. 



Trematoda. — Clean by shaking in a test-tube half full of 

 1 per cent, saline solution ; the dirty liquid having been decanted 

 off, one-third of the tube is filled again with 1 per cent, saline, in 

 which the worms are shaken vigorously, and an equal quantity 

 of saturated HgCl 2 quickly added — the vigorous shaking being 

 continued for several minutes thereafter. This treatment 

 should kill and fix the flukes in an extended position. The 

 parasites may be left in the fixing fluid several days, or they 

 may be transferred immediately to water, washed for twelve 

 hours, and finally stored in 70 per cent, alcohol. 



Large trematodes, sections of which are required for diagnosis, 

 may be treated in the same way, or formalin 10 per cent, may 

 be substituted for the corrosive sublimate as fixing reagent, 

 and a weaker strength, say 3 per cent., used as a storing 

 medium. 



Cestoda. — The strobila are washed gently in 1 per cent, 

 saline, fixed in a solution containing equal parts of saturated 

 corrosive sublimate and 70 per cent, alcohol, to which a few 

 drops of glacial acetic acid have been added — the whole heated 

 to about 50 C. The tapeworms remain in the fixing fluid until 

 it is cold ; they are then washed in running water for twelve 

 hours, and transferred to 70 per cent, alcohol. 



(b) Examination. 



Nematoda. — The worms, preserved in 70 per cent, alcohol, 

 are transferred to a solution made up of 70 per cent, alcohol 

 containing 5 per cent, glycerine. This solution is then placed 

 on a warm plate or incubator at about 6o° C, and allowed to 

 evaporate slowly. The process takes about twenty-four 



