ECHINODERMATA 



421 



a deeper and deeper incision on the part of the lateral depressions.^ 

 (Comj). also in this connection Figs. 200 and 198, as well as Fig. 199 

 A and B.) Joh. Müller figures Auricularians in which the two depi'es- 

 sions almost meet at the anterior end of the larva. Furthermore, the 

 breaking up of the ciliated band discovered by SEM0^^ and the metamor- 

 pbosis of the component parts into the epithelium of the fore-gut men- 

 tioned by him make the band appear to be more probably an oral ciliary 

 ajiparatus, serving for the caisture of food (comp. p. 427). 



The Brachiolarla arises fi-om the Bipinnaria of the star- 

 fish as a subsequent stage by the formation of two addi- 

 tional processes at the base of the longer (dorsal) appendage 

 (Fig. 2U0 -D). In this way are formed the so-called 

 Brachiolarian arms, which are different from the others. 

 They are not bordered by a ciliated band, but possess wart- 

 like elevations at the ends, which probably serve the larva 

 for attachment in later stages. 



In the starfishes, too, many exceptions to the typical form 

 of the larva are found. This is the case in Asterina gibbosa, 

 the development of which has been made known through 

 the thorough researches of H. LuDWio. The larva, which 

 at first is pyriform, acquires a ridge-like thickening, en- 



Fis. 201. — A and B, larvae of Asterina gibhosa (after Ludwig). A, a younger 

 stage seen from in front ; B, older stage seen from the side ; Lo, larval organ ; 

 »/(, mouth. 



closing a depressed area, at the anterior end (Fig. 201 

 Lo). This thickening finally acquires a volume surpassing 

 tliat of the rest of the larval body (Fig. 201 B). The 

 peculiar organ consists of two lobes, and since the anterior 



' [This interpretation is confirmed by the investigations carried on 

 since the above statement was written. — K.] 



