33 



lems. Consequently some important details concerning 

 the method of exposure to low temperatures are often 

 missing. 



H. Weber (1936) could maintain hidl spermatozoa 

 motile in vitro at 0° for 96 hours (Dissert., Leipzig, 1936; 

 quoted from Ber. /. ges. Physiol., 103, 294, 1938). 



According to Spallanzani (1787), frog spermatozoa, 

 frozen hard for half an hour, are able, after thawing, to 

 initiate (^gg development, but if they are kept in the frozen 

 state for several hours, this power is lost. 



The spermatozoa of Periplaneta orientalis (a cocJx- 

 roach), and those of man are capable of surviving freezing 

 for 10 to 11 hours, according to G. N. Pawlow (1927). 



Schenk (1870) reported that the spermatozoa of the 

 frog and of the turtle, frozen at temperatures of -4° to 

 - 7°, resumed motility after being warmed to 38° or 40°, 

 but all attempts to fertilize eggs with these spermatozoa 

 failed. Resumption of motility was also observed on the 

 spermatozoa of rabbits and dogs after exposure to -6°. 



Prevost (C. r. Ac. Sc, 11, 907, 1840) froze excised frog 

 testes at - 8° to - 10°, and then thawed them slowly in cold 

 water. The water was found full of motile spermatozoa. 



Quatrefages (1853) made several observations on the 

 action of cold on fish sperm. His results can be sum- 

 marized as follows : 1. Carp's spermatozoa mixed with ice 

 water on a microscope slide stopped their motion immedi- 

 ately. Barbel's sperm, under the same conditions, main- 

 tained its motility for 50 seconds. 2. Pike's spermatozoa 

 could be observed to be motile after having been directly 

 in contact with ice for 50 hours. In a series of experi- 

 ments in which pieces of ice were put in a dish full of 

 sperm or in which the sperm was stored with ice in a con- 

 tainer devised to allow the water from the melting ice to 

 flow out, the organisms remained motile for 64 hours. 

 3. Pikes, dead for 24 hours and maintained in ice, fur- 

 nished motile spermatozoa, while dead fish kept at 13° to 

 15° showed less viable sperm. 4. Pike's spermatozoa left 

 to freeze overnight either on a plate or wrapped in moist 



