COE: NEMEETEANS OF WEST AND NORTHWEST COASTS. 69 



the burrows in which the worms hve. In such cases two or more 

 individuals of both sexes commonly come together at the time of 

 oviposition. 



It is probable that most species of nemerteans are more strongly 

 gregarious in the breeding season than in other portions of the year, 

 for upward of 50 sexually mature individuals of Micriira alaskensis^ 

 some of which were 300 mm. long, have been found in close contact 

 under a single stone (Coe, : 01, p. 74). 



In most of the Hoplonemertea comparatively few, but very large 

 €ggs are produced, and in some species but a single ovum matures 

 ill each gonad. In some cases this ovum is a third as large as the 

 diameter of the body (Geoxemertes, Tetrastemma), and in the 

 commensal Tetrastemma caecum the few ova produced are about 

 two thirds the diameter of the body. The discharge of such 

 enormous ova must necessaril}' cause serious rupture of the body 

 walls, although it may not cause the death of the Avorm. The eggs 

 of Geonomertes australiensis are described by Dendy ('93) as being 

 about a third the diameter of the body. Several clusters of such 

 eggs are discharged at intervals of a number of days without appar- 

 ent permanent injury to the worm. 



The viviparous Geonemertes agricola gives birth to young worms 

 exceeding in length the diameter of the parent's body, and yet the 

 presence of young ovaries and spermaries indicates that the birth of 

 the yovmg does not cause the death of the parent. 



It is probable, however, that many species are more or less 

 regularly animal, living but a single year and perisliing after the 

 discharge of the sexual products. Other forms probably live for 

 many years. 



Many of the Heteronemertea and some of the Paleonemertea 

 produce an enormous number of eggs of small size, which are dis- 

 charged free into the water. In the large species of Carinella, 

 Taeniosoma, Micrura, Lineus, Euborlasia, and Cerebratulus 

 the number of eggs produced in a single season is enormous. In 

 (Jerebratulus lacteus, for example, a medium sized individual, about 

 5 feet long, has been estimated to produce from fifty thousand to a 

 quarter of a million eggs in a season (Coe, '99''). On this basis of 

 calculation how great would be the number produced by an individ- 

 ual, as has been recorded by Yerrill, 22 feet long and an inch in 

 width ! 



