Notes on the Adult Anatomy of Solaster endeca. 185 



each received the ends of two or three main ducts. Traced inwards these 

 ducts after passing through the body wall divided into branches each 

 of which came into relation with one of the small ultimate clusters of 

 egg tubes (8). 



It is conceivable that in the end eversion of the walls of the pit-like ex- 

 ternal opening might bring the outer extremities of the main egg ducts to the 

 surface, and thus increase the number of external openings. The specimens 

 examined were, however, so large and the ova so near maturity that such an 

 occurrence seems very unlikely. It is much more probable that the condition 

 above described holds good at full maturity and during the actual process of 

 spawning. 



In the case of Solaster papposa, I have only serial sections through the 

 middle of one interradius, in an immature specimen measuring 3^ inches 

 across the disc and arms. In this interradius there are two comparatively 

 wide external openings each leading into a slit-like cavity. Four or five main 

 ducts open into each of these cavities. Traced inwards the ducts have the 

 same relations to the egg tubes as was described above. This observation on 

 Solaster papposa need not be considered as contrary to those of the authors 

 above quoted. The specimen I examined was immature ; the single external 

 opening possessed by each gonad was large and had loose walls, so that 

 there was nothing to prevent eversion of these walls at full maturity with 

 consequent multiplication of the external apertures. Indeed, in his first 

 description, Cuenot also (3, p. 623, note), from the examination of a young 

 specimen, was led to the conclusion that Solaster papposa had only a single 

 external opening for each of the gonads. 



4. Abokal Peeih^emal Sinus (Tig. 7). 



The same series of horizontal sections through part of a large adult 

 Solaster endeca, which I used in studying the relations of the pore canals, 

 enabled me also to follow out the aboral perihaemal sinus in the madreporic 

 interradius, and to note what connections were formed by the haemal tissue 

 enclosed in this sinus, with the axial organ as well as with the genital haemal 

 strands and the two large haemal tufts which pass inwards to the roof of the 

 gastric cavity. 



The points of chief interest brought out by this series are indicated on 

 Fig. 7, which represents the parts as seen from the aboral aspect, the centre 

 of the starfish disc being towards the lower side of the Fig. 



First, in harmony with development and with the more recent teaching on 

 the subject, comes the fact that the aboval perihaemal sinus is entirely shut 



