390 SUMMARY OF CURRENT RESEARCHES RELATINQ TO 



spine formed by the digestive tube ; it occupies just the same position 

 as the sand-canal of Echinids. The swollen upper portions of the 

 other five cords give rise to the chambered organ. The arms do not 

 appear simultaneously, but successively. 



In the Pentacrinoid stage, in which there is no trace of a vascular 

 system, the axial organ retains the histological structure of the ovoid 

 organ of the preceding phase ; the cirri arise from the central cord of 

 the stalk, and the arms from the five peripheral cords. In the last 

 phase, the axial organ, which has the structure of the sand-canal of 

 Asterids and the position of the similarly-named canal in Echinids, is 

 clearly seen to have a nutrient function in relation to the cirri. 



Pharynx of an unknown Holothurian.* — Prof. H. N. Moseley 

 minutely describes the pharynx of an unknown Holothurian belonging 

 to the DendrochirotfB, in which the calcareous skeleton is remarkably 

 developed. 



The specimen was dredged in the Sulu sea, no traces being found 

 of the body to which it belonged. It measures about If in. in 

 length, thus exceeding in size any of the previously known examples 

 with which the author compares and contrasts it. Additional interest 

 attaches to its possible paleeontological significance as the publication 

 of the present account and figure may lead to the recognition of 

 fossil Holothurian remains hitherto undetected. 



Coelenterata. 



Mesenterial Filaments of Alcyonaria.t — The chief results arrived 

 at by E. B. Wilson from a study of the structure and development of 

 the mesenterial filaments in numerous Alcyonaria are as follows : — 



The six short filaments are formed as local thickenings of the 

 septa, the rudiments appearing often before the breaking through of the 

 stomodfeum and " while the invaginated ectoderm was still every where 

 separated from the entoderm by the supporting lamella " ; this shows 

 clearly that these filaments are of entodermic origin, though later they 

 become continuous with the inner ectodermic wall of the oesophagus. 

 It appears from the investigations of the Hertmgs and Krukenberg 

 that these structures are the only organs of digestion, and this result 

 is abundantly confirmed, diatoms and other foreign bodies being 

 continually seen within the substance of the entodermic filaments, 

 and occur within the entoderm-cells covering the sej)ta or the dorsal 

 filaments. 



The two long dorsal filaments, on the contrary, are purely ecto- 

 dermic in origin, being down growths from the stomodfeum ; the 

 structure of these filaments is quite different from that of the ento- 

 dermic filaments ; the dorsal filaments are concerned in the production 

 of currents, the cilia always working upwards. The dorsal filaments 

 are developed earlier and more rapidly in the buds than the ento- 

 dermic filaments, and the reasons for this are to be sought in the 



* Quart. Journ. Micr. Sci., xsiv. (1S84) pp. 255-61 (1 pi.), 

 t MT. Zool. Stat. Neapel, v. (1884) pp. 1-26 (2 pis.). 



