The Influence of the Hatching Factor on the Water Uptake of the Second Stage Larva of the Potato Cyst Nematode Heterodera Rostochiensis

1. Larvae-containing eggs of the potato cyst nematode were soaked in root diffusate in artificial tap water or in artificial tap water alone. In one experiment, the eggs were still contained in intact cysts; in another experiment they were in a halved cyst. 2. Eggs were ruptured after 0–5 days treatment and the water content of the liberated larvae immediately estimated by interference microscopy. 3. Larvae from treated eggs from both the halved and intact cysts had a higher water content than controls. 4. Larvae liberated from treated eggs from the halved cyst reached their maximum water content after 24 h treatment; those from intact cysts attained the same value after 2 days. The delay, for the intact cyst, is in keeping with the hatching response for intact cysts and supports the view that the results for water content are due to the activity of the hatching factor. 5. Reasons are advanced for the view that the hatching factor may work via a neurosecretory mechanism.