INVERTEBRATE ZO :')LOGY. 75 



changes of shape. If the animal is sufficiently qniet, a high power (500^1) may 

 be used. 



42. Preserving and moxnting. Tnrbellaria are among the most diffi- 

 cult animals to preserve. It is almost impossible to prevent their complete 

 contraction upon the application of the customary fixing reagents, and even 

 if this be effected, they are apt to disintegrate or dissolve. If the preserva- 

 tion has been siiccessful, there are many obstacles to success in staining. The 

 integument and body parenchyma stain as deeply as the organs, and thus the 

 internal parts, although we\l stained, are completely hidden. The following 

 methods are an attempt to overcome these obstacles : — 



a. Fixing and jireserving. Use for this Lang's fluid, prepared as follows : 



Water, 100 parts. 



Sodium Chloride, 6-10 " 



Acetic Acid, 5-8 " 



Corrosive Sublimate. . 3-12 " 



Alum, lo " 



Apply it cold, poured suddenly over the anitnal when expanded. Let it re- 

 main in the fiiiid ig-l hour, then in 80 ^. .lO;/, 2-8 hours each and finally in 

 70 % for preservation. 



b. Staining. A successfully stained specimen for mounting in toto should 

 have the separate systems faintly outlined, 'the integument and parenchyma 

 being as nearly colorless and transparent as possible. To effect this, two 

 methods may be used — either to stain very slightly, or to stain deeply and 

 afterwards extract the superfluous color with acid. For the first, use Orth's 

 Lithium Carmine, Alum Cochineal, or Ehrlich's Haematoxylin. a few drops 

 in a beaker full of 70 ^. — extremelj- dihite. Let it remain 1-3 weeks, taking it 

 out from time to time for examination. For the second, use Lithium or Borax 

 Carmine, diluted about one-half, stain 10-li) min. and extract the extra color 

 with acid alcohol (i. e 70;?; + several drops of 10 :r, HCL). Watch this and 

 check the action of the at^id when necessary, by placing in clear 70 f/. All 

 specimens for toto moimting must be flattened before applying the stain. 

 This may be done with a slide and cover, placing the whole under the lens 

 and pressing with a needle handle. A large specimen, if well hardened, niaj^ 

 bear the weight of a slide. Si)ecimens which are to be jirepared for section- 

 ing may be ditt'usely stained without much subsequent withdrawal, and of 

 course should not be flattened. Living specimens, stained in neutral Bis- 

 marck brown, as with Infusoria, show clearly defined nephridia and nerve- 

 cords. 



