THE SYSTEM OF PIIYLLOPIIORIX.E. 



59 v 



internal organization with reference -to the arrangement of tentacles.. 



As to the relation between the notches of radial calcareous 

 segments and tentacular canals, Semper [42, P- 67] has stated for 

 his Thyonidium cebuense ( — Phyllophorus cebuensis) as follows : — „ Der£. 

 Zwischenräumen zwischen den radialen und interradialen Gliedern 

 entsprechen die grossen Tentakel, die kleineren stehen auf kleinen *■ 

 Einschnitten der 1 radialen Glieder, welche einen 3. Ausschnitt für 

 das Radiärgefäss und den Nerv zwischen sich fassen." More precise 

 statements about the relations between tentacular arrangement, the 

 canals and thé anterior notches of radial calcareous segments are 

 found in ÖSTERGREN's work [36, P- 4 with Fig. 1]. According to 

 him, in Pseudocucumis mixta, the canals which join the two smaller 

 tentacles in each radius, pass over slight notches on the two unequal 

 processes of the radial segment. Though no mention is made as to 

 the mode of branching of the four tentacular canals, it can be 

 clearly seen from his figure that each radial canal gives off four 

 tentacular canals in a regularly alternate manner on both sides, and 

 that the smallest branch is given off last and goes over the narrower 

 process of radial segments. Further, the same author has tried to 

 show from Ludwig's figure of the calcareous ring of Orcula tenera 

 [26, Taf. VI., Fig. 17]* that the five small tentacles, which, we see 

 in twenty-tentacled forms, are there totally absent, and that the 

 narrower half of the radial segment is pointed at the anterior end, 

 instead of being notched. The third tentacular canal which stands 

 in connection with each of the five small tentacles, is given off from 

 the radial canal dorsally in paired radii, and to the right in the 

 midventral radius. If we carefully look into the numerous figures 

 given by various authors of the calcareous ring of polychirotous 

 Cucumarids, it will be found that the statements of ÖSTERGREN for 

 P sendociicnmis and Orcida with regard to the relation between the 



* See also Ludwig 25, p. 813, and Taf. XXX., Fig. 20. 



