232 THE GROUSE IN HEALTH AND IN DISEASE 



present in the fresh rain. The plant was then taken from the 

 Petri dish and placed in a cardboard box, which was sealed 

 down. A month later the box was opened. The heather was 

 found to be alive still and growing, but very dry. The tips 

 of the shoots from which the raindrops had been taken were 

 cut off and soaked in little watch glasses of fresh water, and 

 in the course of half an hour there wriggled out from the crevices 

 of the leaves of the heather a considerable number of larvae, 

 showing at either end the long collapsed parts of the sheath 

 which as we have already seen are characteristic of the larvae 

 that have undergone drying under artificial conditions. The 

 intestine showed the characteristic retractile appearance already 

 noted. 



The following synopsis of the life history of this parasite 

 may be of interest as summarising the order and minimal 

 duration of the various stages in the life-cycle. 



April 1. Egg in morula stage passes out of Grouse in soft 



dropping. 

 3. Larva hatches out and lives in dropping of Grouse 



or in moist earth. 

 5. First moult or ecdysis. 

 8. Metamorphosis, larva now in actively migrating 



form. 



9. (or after). Larva ascends to tips of heather; 

 if there is no mist, rain, or dew the ascent will 

 be postponed. 



10. (or after). Encystment or drying ; this represents 

 the first stage of the second moult an indefinite 

 interval may intervene here. 

 10. Larva swallowed by Grouse, and completes second 



moult. 



11. Reaches caeca of Grouse. 



,, 13. Completes the hypothetical third and fourth 

 moults, thereafter become adult and sexually 

 productive. 

 13. Pairs as soon as adult stage is reached. 



