215 



Within the Asteroid-larvae the facts previously made known, together 

 with those given in the present work, decidedly tend to show that there 

 are distinct "family" types of the larvae, corresponding to the families of 

 the adult. Unfortunately, our knowledge is still very limited, so that there 

 is only a poor foundation for the conclusions; but the little we know speaks 

 rather clearly. 



Within the Astropectinidai we know the larvse of four different species, 

 all agreeing in their main features; the processes are very short, rigid, and 

 the larvBe do not develop into a Brachiolaria. By the metamorphosis the 

 whole larval body is absorbed. — Within the Luidiidse we know the larvse 

 of the two species Luidia Sarsi and ciliaris, which both agree so closely 

 in their characters that it is difficult to distinguish them. They are char- 

 acterized by the great elongation of the anterior part of the body which 

 apparently forms an active swimming organ; all the paired arms, which 

 are long and movable, are situated close together in the posterior part of 

 the body. There is no Brachiolaria-stage, and the larval body is not ab- 

 sorbed by the metamorphosis but apparently simply cast off, when meta- 

 morphosis is completed. — The fact that "Bipinnaria aster igera" is re- 

 corded from the Celebes-Sea (in the "Summary of Besults" of the "Chal- 

 lenger", p. 836) indicates that at least one more species of Luidise has a 

 similar larva, which lends support to the conclusion that we have here a 

 distinct larval type, characteristic of the genus Luidia. Whether we may 

 conclude this much that these two larval types represent the larvse of the 

 famiUes of the Astropectinidae and Luidiidae, is, of course, doubtful. But, 

 at least, there is nothing to disprove it. 



Within the other families the few facts known of the development of 

 the Asterinidse and the Gymnasteridse hardly form a sufficient base for any 

 conclusion as to the characters of their larvse. I would only say that the 

 character of the rudimentary larvse of Asterina gibbosa and exigua, com- 

 bined with the fact that the larva of Asterina pectinifera develops into a 

 Brachiolaria, tend to show that within this genus (s. lat.) the larvse typic- 

 ally have a Brachiolaria-stage. 



Within the genus Aster ias the development of the species A. rubens 

 and vulgaris has been studied very completely, and of a third, A. glacialis, 

 enough is known to state that its larva agrees very closely with those of 

 the other two species. It appears that we have here a very distinct larval 

 type, characterized through its long, movable processes, and developing 

 into a Brachiolaria with round arms, crowned by a circle of papillse. On 

 metamorphosis the larval body is completely absorbed. The characters of 

 the young larvse of some other forms, Orthasterias leptolena, Euasterias 

 Troscheli, seem to indicate that these forms also have a Brachiolaria-stage; 



