DIURNAL AND LUNAR RHYTHMS l\3 



inland they are more difBcult to shake out of their inaetivify 

 at periods when the tide is low than at periods when the tide 

 which they have now forsaken is high. Their i)cri()d of rest 

 and sluggishness in the laboratory corresponds to the i)criod 

 of drying up on the seashore. 



A curious example of night and day influence on the i)eriodic 

 movement of birds and mammals is recorded on the coast of 

 Ceylon. Off this coast is a small island frequented by night 

 by crows, and by day by fruit-eating bats or "flying-foxes." 

 The crows fly to the island to rest in its trees at night. In 

 the morning they return to the mainland to feed. The bats 

 fly to the island as daylight dawns to rest for the day sus- 

 pended upside down in rows from the palm leaves. Thus, 

 like Box and Cox in the well-known farce, the same bedroom 

 accommodates both day and night sleepers. 



Fia. 51. Nereis pelagica, a worm belonging to the same sub-order as Eunice 



and Odontosyllis. After Oersted. 



Perhaps one of the most astonishing examples of the state 

 of the moon influencing the movements of animals is afforded 

 by the marine worm known as the Palolo-worm, Eunice^ 

 which lives in the coral reefs of many a Pacific Island. At 

 the last quarter of the moon in October and November the 

 hinder part of the worm, which is crowded with reproductive 

 cells, breaks off from the foremost part, the latter remaining 

 amongst the corals, and the hinder part floating to tlie surface 

 of the sea, where it gives exit to its eggs and spermatozoa. 

 After shedding the reproductive cells this half of the worm 

 dies. The spawning of this half of the worm takes place 

 at low tide on several successive days ; and it is eagerly 

 sought after by the native fishermen, who esteem it a great 

 delicacy. So regular is the appearance of these worms that tlie 

 fishermen know the right time to prepare their boats and 

 nets, and so far they have never been disappointed. Tliere 

 are several other worms of a somewhat similar nature, such as 



SL lO 



