34 



paptT, or in a dish full of water, were acliN'c llic next day, 

 after tliawiiii;'. 5. To kill Piko's sperm l)\' cold, it took 

 a 5-li()iii- exposure of the iee-sperm mixture to a lemi)era- 

 tiire of - 10° to - 12°. In the course of tlu'se expei-imenls 

 it was ()])ser\'ed also that: a. coni])let('ly uiatui'e s])ei'm 

 was less resistant than immature sperm; b. spermatozoa 

 ag'grei»'ated in clumps resisted longer than those dispersed 

 in water; c diluting the material was apparently more 

 injurious than cooling it. 



Mantegazza {Reudir. r. Inst. Lomh., 3, 183, 1866), as 

 quoted from Davenport (1897), reported that human 

 spermatozoa were not killed by exposures to -17°. 



2. Eggs. We shall classify the literature on eggs ac- 

 cording to species. 



Gemmules of 2 kinds of sponges are said by Waltner 

 {Arch. f. Naturgesch., 59, 257, 1893) to have resisted 

 respectively 17 days and 59 days in ice. 



Essex and Magath {Am. J. Eyg., 14, 700, 1931) placed 

 ova of the tapeworm, IJiphgltohothrium latum, in water 

 and subjected them to a temperature of - 10° for 48 hours. 

 This treatment killed them all. 



Zawadowski (1926) reports that fertilized eggs of 

 Ascaris can withstand - 5° for 1 month, and show normal 

 development after subsequent warming. After 14 days 

 at - 20°, 50 per cent of the eggs degenerated ; after 2 

 months of exposure to - 24°, there was still a possibility 

 of development on warming, yet the embryos finally died. 

 An exposure of 1 j years to - 10° produced a similar 

 degree of injury. (From Belehradek, 1935.) 



A wealth of data on the death temperatures of insect 

 eggs is found scattered in the observations of the entomol- 

 ogists of the last two centuries. Bakhmetieff (1901), 

 Bachmetjew (1901) and Uvarov (1931) reviewed the sub- 

 ject. "We refer the reader to these authors' works for 

 more complete information and we mention here only a 

 few of the more striking results. Some of them indicate 

 a high cold resistance, others a high cold sensitivity. 



Spallanzani (1787) observed that the eggs of Bomhyx 

 morl can support an air temperature of -50° for 4 hours. 



