SIGNIFICANCE OF CERTAIN LARV/E OF ECHINODERMS. 17! 



Selenka 1 has studied and figured the larva of Cucumaria 

 doliolmn which, although totally unlike an auricularian larva, can 

 be well compared with a pupa. It is an elongated free swimming 

 creature with four, sometimes five, transversely arranged ciliated 

 rings, in addition to which, at the anterior end, there is a ciliated 

 field. This ciliated field is one of the first of the larval structures 

 to disappear as development progresses. In Selenka's figure of 

 this larva, reproduced in outline in Fig. 3, five tentacles and two 



F--- 





-4 



--- 5 



FIG. 3. Larva of Cucumaria doliolmn. After Selenka. F, tube feet ; T, ten- 

 tacles ; 2, 3, 4 and 5, ciliated rings. 



tube feet are shown to be developed and the rotation of the 

 mouth and tentacles to the terminal position has begun. The 

 eggs of C. doliolmn are quite large and well supplied with yolk, 



1 E. Selenka, " Zur Entwicklung der Holothurien," Zeit. f. wiss. Zoo!., Vol. 

 XXVII., 1876. 



