278 SCIENCE PROGRESS 



the right time to prepare nets and boats for the catch by the 

 state of the moon. It is not known what gives the stimulus to 

 the worms to spawn, whether moonhght, tide, or some other 

 physical change depending on the moon. 



In Japan there is another Palolo {Ceratocephale Osawai) 

 which swarms both at full and new moons (Izuka, Journ. Coll. 

 Set. Tokyo, 36, 1903). Here the bilunar periodicity is pre- 

 sumably due to the spring tides, but we are ignorant of the 

 manner in which the greater tidal range may react on the 

 animals. In the Atlantic yet another kind of Palolo {Slauro- 

 cephalus gregaricus) swarms usually at the last quarter, but 

 occasionally also at the first quarter of the moon (Mayer, 

 Carnegie Inst. Pub., 102, 1909). Mayer was the first to abandon 

 the observational method which had proved so unfruitful in 

 seeking for a causal explanation of lunar periodicity in repro- 

 duction. He carried out direct experiments. Eleven mature 

 worms were placed in a floating {i.e. tideless) box thirty days 

 before the swarming time was due. Only four of these worms 

 swarmed, whereas in nature all mature individuals swarm. 

 Thus the tide appears not to be the sole cause of swarming, 

 unless, of course, those worms which swarmed in the floating 

 box did so owing to a tidal rhythm previously acquired, as in 

 the case of Convoluta mentioned above. Mayer also put 

 twenty-two worms in floating boxes protected from the moon- 

 light. None of these animals swarmed. The light seems 

 therefore to be a necessary contributory cause for swarming. 

 These valuable experiments should be repeated with a greater 

 number of individuals. It is obvious, however, that whether 

 light, tide, or some other factor gives the worms the stimulus to 

 leave their holes in the rocks and swim up to the surface, some 

 influence which varies with the lunar period must affect the 

 worms at a date long anterior to the swarming time. For in 

 order that all the worms should be sexually mature and ready 

 to swarm together at, say, the last quarter of a certain moon, 

 the development of the genital organs must have been initiated 

 in all of them together at some definite previous lunar phase. 



There are certain other marine worms which show a lunar 

 reproductive periodicity. Potts found that sexually mature 

 individuals of Odontosyllis in British Columbia swarm once a 

 year from the sea-bottom to the surface in order to spawn. 

 This occurs in August, during the first or third quarter of the 

 moon (Proc. Camb. Phil. Soc, 17, 191 3). At Bermuda this worm 

 also exhibits a lunar periodicityin swarming. Another Polychaete, 

 Nereis, at Woods Hole, Massachusetts, swarms at sunset through- 

 out the summer months, but during the waning phases of 

 each moon only (LilHe and Just, Biol. Bull., 24, 191 3 ; and Just, 

 Biol. Bull., 27, 1 91 4). At Naples Nereis swarms round about 



