464 BOUNDARIES OF THE SEA 



life of 15-16 weeks. The longest larval life among asteroids seems, 

 however, to be found in some species of the genus Luidia. Thus, 

 the larva of Luidia sarsi may attain the remarkable length of 

 25-35 mm (Mortensen, 1901) and seems fit for a long pelagic life, 

 the duration of which has not been ascertained thus far. For 

 Luidia ciliaris, the egg number of a single female has been calcu- 

 lated at 200,000,000 at least (Mortensen, 1913), a figure which 

 suggests a heavy loss of larvae, and this again is normally closely 

 associated with a long planktonic stage. In accordance with these 

 suggestions it seems reasonable to point out that a species of 

 Luidia (L. senegalensis) actually is found on both shores of the 

 tropical Atlantic Ocean, off Senegal and oft" Brazil (Hyman, 1955). 



This distribution pattern seems to lose its value as an argument 

 when we realize that a fair number of ophiuroids are also common 

 to West Africa and the Antilles (Hyman, 1955). Figure 1 shows 

 that of the ten species of ophiuroids examined so far, all tend to 

 have a very short pelagic life. To explain this apparent contra- 

 diction, I should like to call attention to some observations on 

 larval asteroids and ophiuroids, so far disregarded by all textbooks, 

 but probably of great importance. In 1906 Delap observed that 

 the giant, 25-35 mm long, larval body of the sea star, Luidia sarsi, 

 survived for at least 3 months after the young bottom stage had 

 developed from it, metamorphosed, and settled. In most other 

 asteroids the larval body will not exceed 2 mm in length, and a 

 biologist rearing asteroid larvae will hardly pay any attention to 

 the larval body after the settling of the young bottom stage. In 

 Luidia, the larval body is so conspicuous that one may hardly 

 disregard it, and it has been found to live for at least 3 more 

 months. This was confirmed by Tattersall and Sheppard (1934). 



Still more surprising is a discovery made by Mortensen (1921), 

 carefully hidden in his long paper on echinoderm larval develop- 

 ment. In it (pp. 147-149) he describes an ophiuroid larva, Ophio- 

 pluteus opulentus, from Thailand which, in his rearing dishes, after 

 it had produced and given off one young bottom stage, regenerated 

 its ciliary bands, its mouth, and esophagus to look like a com- 

 pletely normal larva before the development of the young bottom 

 stage set in. Since Mortensen was a most reliable and careful 

 observer, I should like to quote him. He concludes this exciting 



