142 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



rina has led me to support the view advanced by Tiede- 

 mann, Miiller, Agassiz, and much more recently by 

 Ludwig, viz., that all the pores which traverse this plate 

 open directly into the water-tube (PI. XXXVI, fig. l,m2J), 

 Hoffmann, supported by Greeff and Teuscher held on the 

 other hand that some of the marginal pores open into the 

 coelom, and others into the axial perihaamal canal. A 

 condition of things differing from either of the latter is 

 presented by one of my series of sections, cut from the 

 disc, 6 mm. in diameter, of a specimen of Asterias ruhens. 

 In this three or four of the madreporic pores opens directly 

 into the lacunar system of the body-wall (PI. XXXVI, fig. 2). 

 In young specimens of Crihrella, 2 mm. in diameter, 

 Durham (1) found but a single pore opening into the 

 cavity of the axial perihsemal canal, into which the water- 

 tube also opens ; and Cuenot (2) shows that in some species 

 this state of things may continue throughout life. 



Communicating with the exterior through one of the 

 madreporic pores in the specimen just alluded to is an 

 elongated glandular structure, lodged in one of the lacunae 

 of the body wall (PI. XXXVI, fig. 2, gh). It is composed 

 entirely of small rounded cells with comparatively large 

 nuclei, and does not present any cavity or lumen. I am 

 not at present able to offer an opinion as to whether this 

 organ should be regarded as an example of the structure 

 described by Greeff and Ludwig, and alluded to by Carpen- 

 ter (3) as a diverticulum of the water-tube, or as an 

 . independent and perhaps hitherto undescribed structure. 

 It is certainly independent of the water-tube, through 

 lying in close proximity to it. Still more perplexing is 

 its occurrence in only one specimen out of a dozen carefully 

 examined. In its passage downwards to the oral aspect 

 of the disc, the water-tube is supported by the free edge 

 of a projecting fold formed by the junction of the rays on 



