NOTES ON L.M.B.C. ASTEKOIDEA. 145 



haemal ring (PL XXXVIII, fig. 2 ; PL XXXIX, fig. 1, ahr) 

 from which arise the ten genital strands {gs), two at each 

 interradius. Cuenot's (6) studies of the development of 

 the genital organs of Asterids have led him to the conclu- 

 si(?n 'tlrnt they are simply the largely developed ends of 

 the genital strands, and that the cells of the strands give 

 rise to ova or spermatoblasts. With the exception of the 

 gastric strands, the whole haemal system is enclosed in 

 perihsemal canals, with which the axial perihsemal canal 

 is continuous. I have already said that at its oral end the 

 central plexus becomes continuous with an oblique per- 

 forated septum. This latter imperfectly separates the 

 circum-oral perihsemal canals, into the inner of which the 

 axial perihaemal canal opens, while the outer unites the 

 perihsemal canals of all the rays (PI. XXXIX, fig. 1, ipc, 

 ope). Serial sections in which the septum appears show 

 that at many points it presents lacunar spaces to wiiich 

 the term " oral blood-vascular ring " has been applied (PI. 

 XXXVIII, fig. 3, cohr), the lacunae being described as 

 vessels. They are, however, simply lacunar spaces, and 

 except when distended with coagulum, or with amoeboid 

 cells, are not easy to see. It has been asserted that they 

 and the haemal lacunae of the rays are nothing more than 

 spaces occupied before decalcification of the specimen by 

 calcareous skeletal matter. I am satisfied, how^ever, that 

 such is not the case, for the connective tissue basis upon 

 which the skeleton is formed is always left intact after 

 decalcification, and no such connective tissue is seen here. 

 The perihaemal canals of the rays are, like the circumoral 

 canals, imperfectly separated by a vertical septum which 

 is continuous with the oblique septum already described. 

 These also present lacunar spaces, frequently distended 

 with coagulum, or with amoeboid cells, and are the radial 



