270 RECORD OF CURRENT RESEARCHES RELATING TO 



muscles ; but no branches are traceable from the ambulacral nerves 

 on to these muscles such as are known in the Ophiurids. 



Dr. Cai'penter's experiments at Naples have shown that these 

 muscles are under the influence of a governing centre, which not only 

 regulates their contractions, but co-ordinates those contractions in the 

 most remarkable manner; and that this centre is situated in the 

 fibrillar envelope of the chambered organ, while the axial cords of 

 the rays and arms are the channels by which the influence of the 

 centre is communicated to the muscles. 



This experimental evidence as to the nervous nature of the axial 

 cords is further supported by the results of anatomical investigation. 

 Sections show that these axial cords give ofi" branches regularly in 

 the centre of each segment of the arms and pinnules ; and that while 

 some of them ramify upon the ends of the muscular bundles, others 

 are traceable into the small marginal leaflets bordering the ambu- 

 lacral grooves, where they break up very minutely and become lost. 

 It has also been discovered that in many tropical Comatulce which 

 have an excentric mouth, more or fewer, sometimes even more than 

 half the arms which come off from the aboral side of the disk, have no 

 ambulacral nerve at all, although the dorsal axial cord gives off its 

 two pairs of branches in the usual way. In one large species from 

 the Philippines with nearly two hundred arms this condition is not 

 limited to the aboral arms only, but occurs on some of the arms on 

 each radius, while the others have the usual groove and subjacent 

 ambulacral nerve. 



These facts are strongly indicative of the nervous nature of the 

 axial cords, although Glaus and Gegenbaur in their recently pub- 

 lished text-books make no mention of this view at all, and described 

 the nervous system of Comatula as essentially similar to that of the 

 star-fishes. It would seem, however, that while the ambulacral nerve 

 of the Ophiurids supplies the muscles as well as the tentacles, these 

 functions are more differentiated in the far more active Crinoids. 

 The axial cords of this group appear to be the principal motor nerves 

 as far as the skeleton is concerned, while the ambulacral nerves 

 supply the tentacles only, possibly having some influence on the slow, 

 creeping movements which the isolated disk has been observed to 

 perform. Why should we deny the nervous nature of the axial cords, 

 simply because our doing so would clash with our preconceived 

 notions as to what the Crinoids ought to be in order to agree with the 

 views on Echinoderm morphology, which were adopted without a 

 sufficient knowledge of the anatomy of this most interesting group ? 



Development of Asterias rubens.* — Dr. Greef finds that after 

 the unimpregnated ovum of the Star-fish has been in fresh sea-water for 

 five or ten minutes the germinal spot becomes granular. The granules 

 are at first rare and small, and appear at the periphery and around 

 the central vacuole ; they increase rapidly in number, and the spot 

 takes on a mulberry-like appearance. The small granules now 

 increase rapidly in size, and as they grow they gradually fuse with 



* ' Arch. Naturg.,' xlvi. (1880) p. 94. 



