SOME OBSERVATIONS ON THE HATCHING OF TORTANUS DISCAUDATUS EGGS SUBJECTED TO LOW TEMPERATURES 1

Eggs of Tortanus discaudatus, a calanoid copepod, were sorted from the plankton at Friday Harbor, Washington, and set up in cultures subjected to temperatures ranging from 12.5C to −2C to observe the hatching rate and viability at low temperatures. At the higher temperatures, the eggs hatch in three to four days. Hatching goes on slowly at 0C, and of 20 eggs held at −2C, one hatched in 17 days and 53% of the remaining eggs hatched in five days when returned to 11.5C after an exposure of 30 days. Thus, the eggs were viable after at least one month at −2C.