362 



p. HERBERT CARPENTER. 



by liim to reappear in the larval forms of the modern 

 Articulate Crinoids. This hypothesis appears to me to be 

 not only unnecessary but also absolutely incorrect, and for 

 the following reason. 



I have already shown^ that there is every reason to believe 

 in the general existence of a " chambered organ " in most 

 if not in all the Articulate Crinoids. It is contained in a 

 special cavity at the base of the calyx, the exact position of 

 which varies in different genera. But whatever its position, 

 the basals are invariably perforated or grooved for the pas- 

 sage outwards of the five primary fibrillar cords from the 

 interradial angles of the chambered organ (fig. iv, 3, 3). 



Fig IV. — Calyx of Enerinus. (After Beyricb.) 2, Under-basals. 3. 

 Basals. 4. (First) Radials. ax. Radial axillaries. 



The dark black lines show the arrangement of the canals, 

 which lodged the branches of the five primary cords, pro- 

 ceeding from the interradial angles of the chambered organ. 

 These cords bifurcate within the basals, and the ten 

 secondary cords resulting from this bifurcation proceed on- 

 wards to the circular commissure contained within the 

 circlet of radials (fig. iv, 4, 4). This character, the pre- 

 sence or absence of bifurcating grooves or canals, gives us 

 the means of at once determining with accuracy the position 

 of the basals in the calyx of any Crinoid. I have already 

 drawn attention to the presence of a chambered organ in 



' ' Pentacrhms and Rhizocrinns,' loc. cit., p. 42. 



