THE INVERTEBRATE LEGIONS 109 



The species of this class are extremely common in all seas. They may be 

 rather neatly divided into three groups on the basis of habits— errant or wander- 

 ing species, burrowing species, and tube-dwelling species. 



1. Errant Polvchaetes. These marine worms are the most common. They are 

 the most active worms and are armed with a jaw-bearing pharynx which 

 can extend and retract for the capture of living prey. Some of them can 

 swim, but most are found secreted under stones, among weeds, and other- 

 wise hidden from their many enemies which relish their soft bodies for 

 food. The breeding habits of some errant polychaetes are amazing. Most 

 famous is the palolo worm, Eunice, one species of which is found in the 

 South Pacific and another in the West Indies. During the last quarter 

 of the October-November moon in the South Pacific or the third quarter 

 of the June-July moon in the West Indies, the bottom-living palolo 

 breaks off its tail (Borradaile and Potts, 1935). The tail, ripe with either 

 eggs or sperm, then swims to the surface of the water, where thick swarms 

 of these reproductive tail ends occur. When eggs or sperm are released, 

 the tail, now an empty bag, dies and sinks to the bottom. Meanwhile, the 

 original head end of the worm on the bottom regenerates a new tail which 

 becomes reproductively ripe the following year. 



Swarming of breeding individuals at the water's surface is common in 

 errant polychaetes. It insures fertilization of a maximum number of eggs 

 since many worms are grouped closely together. Some swarming worms emit 

 a light so that the females and males can more easily find each other. Others 

 have the remarkable ability to bud off new individuals from the posterior 

 end of the bodv- Each of these individuals can breed but cannot feed since 

 it has no mouth parts. Sometimes a long chain of budding worms may be 

 found at the water's surface during the breeding season. Two of these 

 budding types are Syllis and Autolytus, both of wide distribution and 

 growing about an inch in length. 



The sandworm. Nereis, is perhaps the most familiar of errant polvchaetes. 

 There are great numbers of worms found the world over that look like 

 this worm. Some are well over a foot in length, and the larger ones can 

 give a painful bite with their strong jaws. 



The sea mouse. Aphrodite, is a mud-dwelling, stout-bodied, very beautiful 

 species with long, silky, iridescerit bristles. It reaches 4 inches in length. The 

 scale worm, Lefidonotus, reaches 2 inches and is common under stones 

 near shore. These are both stout worms of wide distribution which stay 

 near the bottom. 



One family of errant polychaetes deserves special mention because of 

 the stinging powers of its bristles. This is the Amphinomidae, or the silky 

 bristle worms. There are several species, all of which have long, detachable 

 bristles that easily penetrate skin and cause a burning sensation. These 

 bristles are hard to remove. Phillips and Brady (1953) suggest removing 

 the bristles with adhesive tape. The most common bristle worm is Henno- 

 dice of tropical waters. It often reaches a foot in length and is warningly 

 colored with red marks on the sides. The white bristles tipped with 



