LEODICIDjE OF THE WEST INDIAN REGION. 



45 



he figures minute denticulations which I did not find. He figures also two of the gills 

 with branching filaments which are described above. Mayer later (1902 and 1908) 

 added some details to Ehlers's description, and published colored figures of the animal. 

 In another paper (1900) he also figured several of the larval forms. 



The animals live in crevices of the coral rocks, protruding the anterior ends for 

 feeding, but the remainder of the body is never exposed to the open water except at the 

 breeding season. On the approach of the breeding season the body becomes much 

 distended with eggs or sperm and assumes the characteristic color. (See above.) At 

 this time it is extremely sensitive to contact, so that while it is comparatively easy to 

 get good specimens of immature forms, mature ones, on being taken from the rock and 

 on the first contact with sea-water or preserving fluid, begin active writhing movements 

 which are usually strong enough to break the body in pieces, the sexual ends often 

 going through movements quite like those of the normal swarming. 



That L. fucata swarms at the breeding season was discovered by Mayer (1900), 

 though he was in error in the identification of the species. This error is repeated by 

 Mclntosh (1910, p. 352), who, overlooking Mayer's correction, speaks of a swarming 

 Staurocephalus. Later (1902), Mayer gave the correct identification and named the 

 animal the Atlantic palolo because of the similarity of the swarming habit to that of a 

 related species, Leodice viridis, of the Pacific. On the night or nights of the swarm the 

 animals protrude the posterior ends of the bodies from the rocks and, by an anti- 

 clockwise movement, break them off at the junction between the sexual and non-sexual 

 portion. The sexual portion swims rapidly to the surface, usually reaching there about 

 daylight. In an ordinary swarm the number of these ends to be seen floating in this 

 way at daybreak is very large, there being hardly a square foot of the surface in which 

 one is not to be seen. Just at sunrise the thin body-wall bursts, setting free the eggs 

 and spermatozoa, and the eggs are at once fertilized. The eggs are large and float at 

 the surface, where they undergo their early development. According to Mayer (1900, 

 p. 7), they settle to the bottom on about the fifteenth day after fertilization, but for 

 some days previous to this specimens in an aquarium could be seen in water of all depths. 



This swarming usually occurs in coincidence with the last quarter of the June-July 

 moon, though if the last quarter of this moon comes late in July, there may be a swarm 

 in connection with the first as well as with the last quarter (Mayer, 1908, p. 108). In 

 addition to the main swarm, there may be a smaller one on either the day before or the 

 day after the principal one. As a footnote to a report by Treadwell (1914, p. 221), 

 Mayer published the following table showing the recorded dates from 1898 to 1914: 



Dates on which the Atlantic palolo has been observed to swarm at Torlugas and dates of the quarters of the moon. 



The date of the principal swarm is shown in italics, while the dates upon which only a few worms 

 are observed swarming are shown in ordinary type. 



