488 Mtscellaneous. 



we find in Cucumaria crocea, Less., where, moreover, the young are 

 borne not on the ventral but on the dorsal surface, ambulacra do not 

 have to assist in the care of the brood. The young are attached 

 close together in a single layer to the median area of the creeping 

 sole, which is hedged round by the pedicels ; if they be detached, 

 the spots they previously occupied are indicated only by slight 

 impressions. 



The young average but I'o millim. in length and barely 1 millim. 

 in breadth, but are nevertheless already well developed, so that they 

 represent a tiny copy of the adult animal. The arched dorsal 

 surface already possesses a closed armature of imbricated calcareous 

 plates, among which the five oral plates can clearly be distinguished. 

 In their development these dorsal plates pass through a stage which 

 is retained permanently by the calcareous bodies in the ventral 

 integument of the adults. The flat ventral side is encompassed by 

 a single (not yet double) series of twenty pedicels, which are already 

 equipped with a relatively large terminal disk and some supporting 

 plates. These pedicels develop later on into the inner series of 

 larger pedicels which we find at the margin of the ventral surface 

 of the adults, while as yet there have appeared no rudiments of the 

 series of much smaller external pedicels. In the ventral integu- 

 ment the formation of the calcareous bodies has only just begun. 

 In the calcareous ring there can already be recognized five radial 

 and five interradial pieces, similar in form to those in the adults ; 

 towards the radialia there already extend distinct retractor muscles. 

 Moreover the full complement of tentacles (ten) is already present, 

 and they contain in their walls a few small cribriform plates. A 

 calcified madreporic plate belonging to the stone-canal is developed. 

 The intestine is coiled in the same way as it is subsequently. Of 

 respiratory trees, however, no rudiments appear yet to have come 

 into existence, nor can I yet observe any trace of the genital organs. 

 The number of Holothurians which care for their brood conse- 

 quently now amounts to nine, including five antarctic and one 

 arctic species. Not only is the relatively large number of the 

 antarctic forms exceedingly striking, but almost even more remark- 

 able is the circumstance that in each of the five antarctic species 

 the care of the brood is effected in a different way. In Psolus 

 ej^liipplfer the young develop beneath the dorsal plates, in Cucu- 

 maria crocea upon the modified dorsal ambulacra, in Psolus ant- 

 arctkus upon the ventral creeping sole, in Cncnmaria hn-ir/ata in 

 ventral brood-pouches, and, lastly, in the case of Chiridota contorta 

 in the genital canals. — Zoologisclier Anzeiyer, Bd. xx. no. 535 

 (July 5, 1S97), pp. 237-239. 



