220 



Exporimonts \vitli ciliates smalU'r than paramocia, that 

 is, with oolpoda, in tlio vrgotativr state, likewise uavo 

 negative rosnlts. 



The same is true also ot' experiments with amoebae. 



(hi the whole, onr investigations on the three principal 

 groups of protozoa, the rhizopods, the eiliates and the 

 tlagellates, did not allow us to revive a single organism. 

 It seems probable that these animals oould not really be 

 vitritied on account of their too high water content. 



However, revival was obtained in some experiments with 

 myxamoebae (Gehenio and Liiyet, unpublished). Out of 

 thirty attempts made to vitrify these organisms by immer- 

 sion in liquid air on the wire loop, live gave living 

 myxamoebae whose contractile vacuoles resumed their 

 function and maintained it for several lionrs. Though the 

 percentage of animals revived is small, we consider the 

 fact as highly signiticant. 



Next we tried the spermatozoa of the frog (Luyet and 

 Hodapp, 1938c). A smear on a thin cover-glass gave nega- 

 tive results. A second attempt on a sheet of mica was 

 no more successful. A third series of experiments in 

 which the spermatozoa were previously immersed in a 

 20% sucrose solution for being dehydrated before immer- 

 sion in liquid air, yielded some motile organisms, less than 

 l^c of the number treated. By incri'asing the concentra- 

 tion of the sucrose solution to 40' < or 507^, we could 

 increase the percentage of motile or non-disorganized 

 forms to 20/( or more. To sum up, by employing with 

 the spermatozoa of the frog the method of mica sheets, of 

 dehydration in concentrated sugar solutions and of rapid 

 warming in water at 20°, we obtained some living forms 

 in each preparation. 



Studies on the duration of immersion in liquid air which 

 the spermatozoa can support have shown that the number 

 of survivors and their activity are the same after live days 

 as after three seconds. This finding is in good agreement 

 with the assumption that the material is vitrified and stays 

 unaltered at low temperatures. 



