SIGNIFICANCE OF CERTAIN LARVAE OF ECHINODERMS. 1/3 



apical tuft of longer cilia is also present. Seeliger's ' figure of it 

 is reproduced in outline in Fig. 4. No pore canal is developed 

 at this stage but the point on the hydrocoele at which it will ap- 

 pear later, I have indicated by a small x. 



Ophiurids. 



For a long time the larvae mentioned above were the only ob- 

 served cases in which the ciliated bands are arranged in trans- 

 verse rings, and they were considered to have no special signifi- 

 cance. Since 1899, however, I have found three other cases 



^"""^rviTr "- 



FIG. 5. Ventral view of the young larva of Ophiiirn brevispina. Original. 2, 

 3, 4 and 5, ciliated rings. 



which exhibit the same peculiarity and which represent two other 

 classes of echinoderms. 



The larva of Ophinra brcvispina, which I 2 described in 1899, 

 is well supplied with yolk and very early in its development it 

 sinks to the bottom and clings to grass blades where it under- 

 goes its late larval stages and final metamorphosis. It is a larva 

 without arms or processes of any kind and no skeletal rods such 



1 O. Seeliger, " Studien zur Entwicklungsgeschichte der Crinoiden," Zool. Jahrb., 

 Bd. VI., 1892. 



2 Caswell Grave, " Ophiura brevispina," Mem. Natl. Acad. Sci., 1900. 



