Notes on the Adult Anatomy of Solaster endeca. 175 



of the lateral lobes of the ampulla of the stone canal had an opening into the 

 axial sinus ; (b) most of the madreporic pores passed into collecting canals, 

 which opened into the madreporite, but some few led into the upper extremity 

 of the axial sinus. Durham mentioned incidentally in this connection that his 

 observations in Asterias ruhens agreed with the view of Ludwig given above, 

 and he considered the condition he found in Cribrella to be probably abnormal. 

 Perrier (5), in very young Asterias spirabilis, found an aperture connecting 

 the upper end of the stone canal with the axial sinus. Macbride (6) states 

 that the axial sinus has an opening into the stone canal, and also com- 

 municates by pore canals with the exterior. 



Goto (7) would distinguish, as separate from the anastomosis described 

 by Cuenot, a special opening underneath the madreporite on the dextral 

 side of the commencement of the stone canal. The latter opening he finds 

 in Asterias pallida, Asterias tenera, Asterina gibbosa, Solaster endeca and 

 Cribrella sanguinolenta, and he considers that it represents the primitive 

 connection between axial sinus and stone canal existing since larval life. I 

 find a similar opening in young specimens of Asterias rubens, L., Solaster 

 papposa, L., and Porania pidvillus (O.F.M.), but, as will be indicated below, 

 I believe that the channels of Cuenot and Goto's opening belong to the same 

 system, the latter, at any rate in the fully-grown S. endeca, being broken up 

 into a large number of apertures, all of which are embedded within the 

 madreporite. This view is in general agreement with Cuenot's comparison 

 of the relation of these parts in other starfish and Echinoderms. 



I had available for study a very good horizontal series through the 

 madreporic interradius of a specimen of Solaster endeca measuring 7 inches 

 across disc and arms. 



The pore canals are very numerous, amounting to over four hundred. 

 Those near the middle of the madreporic surface pass vertically downwards, 

 but the marginal ones slope slightly towards the centre of the madreporite. 

 At their external orifices, and for a short distance inwards, the lining of all 

 of them is made up of strongly ciliated columnar cells, while farther in, it 

 consists of cubical weakly ciliated epithelium, not much stronger than that 

 forming the general lining of the axial sinus. 



As they pass inwards, the pore canals unite in small groups on a common 

 stalk. Deeper down, adjacent stalks also unite to form larger collecting 

 branches, between which a fairly free anastomosis may be found. 



The collecting branches which are in relation with the pore canals 

 occupying the middle area of the madreporite, open directly into a small 

 horseshoe-shaped central chamber lying within the substance of the madre- 

 porite, and to be afterwards described. On the other hand, the collecting 



