222 M. A. Baur on Synapta digitata 



of cilia) into which these larvae are transformed coincide most 

 in their anatomical structure with the footless and abranchiate 

 section to which the genera Chirodota and Synapta belong. They 

 retain, in the skin at the posterior extremity of the body, the 

 peculiar calcareous structures of the larva. 



For the more precise determination of one of these larval 

 forms, and the corresponding young Holothurid,with the globules 

 and the calcareous star, J. Miiller possessed no data [loc. cit, 

 1849, p. 55). In the other, the occurrence of the calcareous 

 wheels still at the posterior extremity of the young Holothurid 

 could not but lead to the supposition that it belonged to the 

 genus Chirodota (ibid. p. 49), because this genus has calcareous 

 wheels in the skin, whilst the nearly allied and anatomically 

 accordant genus Synapta has little anchors inserted into a per- 

 forated calcareous plate. 



Grube has described two Holothurids of the genus Chirodota 

 from the Mediterranean — Chirodota Chiaji and C. pinnata 

 (' Actinien, Echinodermen und Wiirmer des adriat. und Mittel- 

 meers,^ 1840). It has, however, been found that these two, from 

 their zoological characters, namely, the calcareous armature, are 

 not ChirodotcB, but Synapta, and that Chirodota Chiaji, Gr. {Holo- 

 thuria digitata, Mont.), and Chirodota pinnata^ Gr. (Holothuria 

 inharens, O. F. Miill.), must receive the generic name of Synapta 

 (Miiller, Archiv, 1850, pp. 115, 135, 136). One of them is 

 Miiller^s Synapta digitata, and the other Synapta inharens, the 

 latter again being probably identical with Synapta Duverncea of 

 Quatrefages. 



As no true Chirodota, no Holothurid with calcareous wheels, 

 is yet known from the Mediterranean, there were two possibilities 

 in regard to the origin of the Auricularia with calcareous wheels. 

 Either it belonged to a true Chirodota peculiar to the Mediter- 

 ranean, but still unobserved ; or the calcareous wheels in the skin 

 of the larva and young Holothurid could only be transitory 

 structures, and other calcareous structures must subsequently 

 make their appearance in them (Abh. der Akad. der Wiss. 1849, 

 p. 50). The former was the less probable, because, from the 

 abundance of the Auricularia with calcareous wheels, it could 

 scarcely be supposed to belong to a still unknown and there- 

 fore certainly rare Holothurid ; but in the latter case the abun- 

 dant and widely distributed Synaptce must be taken into con- 

 sideration. The decision of the question depended on tracing 

 the young Holothurids produced from the larvae with calcareous 

 wheels (which, in the latest stage seen by J. Miiller, still moved 

 by swimming with their bands of cilia) in their further growth 

 and changes, but especially with respect to the appearance of 

 calcareous structures in other parts of the skin. 



