46 LEODICID^ OF THE WEST INDIAN REGION. 



Treadwell (1915, p. 220) reported that the 1915 swarming occurred on the morning 

 of July 1, the last quarter of the moon faUing on the 3d; Mayer (1916, p. 178) recorded 

 in 1916 an unusual swarm, in that while the larger swarm came on July 20, the day of 

 the moon's last quarter, there was another but smaller one on the day of the full moon, 

 July 14. To Dr. Mayer I am indebted for the information that in 1917 there was a dense 

 swarm on the morning of July 8, with a smaller one on the 9th, the moon's last quarter 

 falling on the 11th. The only certain record I have of a swarming of this species elsewhere 

 is in a personal communication from Mr. Engelhardt, of the Museum of the Brooklyn 

 Institute, who observed it at Andros Island in the Bahamas on June 12, 1914, the date 

 of the moon's last quarter being June 15. Mr. Engelhardt collected some of the swimming 

 ends, which I have identified as this species. It will be noticed that, while the time 

 of swarming bears the same relation to the moon's phases in the Bahamas as it does in 

 the Tortugas, it occurred in 1914 on a different month in the two localities. 



In 1921 the last quarter of the June moon was on June 28. On June 29 I found 

 sexually mature individuals in Montego Bay, Jamaica, but on the following mornings 

 was unable to discover any swarming. Early in the following week a native fisherman 

 told me that worms swim at the surface but only at very rare intervals, that they appear 

 "early in the morning and as the sun gets hot they fade away," and that the last swarm- 

 ing he had known was "last week." Specimens which I collected at this time had lost 

 their posterior ends. This seems to justify the inference that probably they swarm in 

 Jamaica at the same time as in the Dry Tortugas. 



That the Pacific palolo, Leodice viridis, swarms in a definite relation to the moon's 

 phases in October and November has long been known, and considerable literature has 

 appeared in this connection. Later, similar swarmings have been described in species 

 of the Nereidse by Izuka (1903), Hempelmann (1911), and Lillie and Just (1913), and in 

 the Syllidse by Galloway and Welch (1911), these agreeing with the Leodicidse in occur- 

 ring in coincidence with certain phases of the moon, but differing from them in that, 

 instead of being limited to once a year, they may occur on several months in succession. 

 That this rhythm has been set up in the race as a consequence of a long-continued tidal 

 or light stimulus operating in a rhythmical manner is possible. Experiments recorded 

 by Mayer (1908, p. 110, and 1909, p. 3) and Treadwell (1909, p. 139) showed that keep- 

 ing the animals in a floating light-proof live-car where tidal and light stimuli were absent 

 did not prevent the swarming at the regular time. The experiments were not, however, 

 very conclusive, since it is not possible to keep the animals in a normal condition for 

 more than a few days (Mayer kept them for 30) in such a live-car and it is hardly to be 

 expected that if a rhythm had been fixed it would have been modified in so short a 

 time. That an internal stimulus may also be at work was proved by Treadwell (1914, 

 p. 222), who showed that there is a measurable increase in the elimination of CO, by 

 the egg itself as it approaches maturity, indicating an increase in the rate of metabolism 

 at this time, and this might, through increased elimination of waste products into the 

 body-cavity, act as a stimulus to egg-laying. It seems to be evident that while more 

 spectacular than the reproductive rhythms in other animals, this swarming is essen- 

 tially similar in all cases and may be explained in the same way. Thus far no adequate 

 explanation has appeared. 



Leodice fucata has thus far been recorded from the Dry Tortugas, Porto Rico, 

 Cape Florida, and the Bahamas. In the two former localities I found it the most abun- 

 dant of the Leodicids living in the dead, porous coral rock below low-tide mark. I 

 have no data on the greatest depth at which it occurs, my material having been col- 

 lected only as far down as it was feasible to break off and carry home the large pieces of 

 rock. Ehlers records it from 5 to 7 fathoms in Tortugas Channel. My Bahama record is 

 based on the specimens of swarming ends sent me by Mr. Engelhardt; the U. S. National 



