PHORONIS AND ACTINOTROCHA 



recently been published by Ikeda, 1 de Selys Longchamps, 2 Good- 

 rich, 3 and Schultz, 4 who criticise many of Mastermaii's state- 

 ments. While it is admitted 011 all sides that an oblique septum 

 following the line of the bases of the tentacles completely sub- 

 divides the body-cavity, Masterman's account of the anterior 

 cavities is not confirmed, the spaces indicated by b.c 1 and b.c' 1 in 

 Fig. 14 being stated to be really continuous with one another, 

 while the " subneural sinus " (s.s) is regarded as a part of this 



FIG. 14. Actinotrocha-larva. of Phoronis. a, Anus ; 

 b.c 1 , b.c' 2 , b.c 3 , first, second and third body-cavities ; 

 c, circular nerve, running in the posterior boundary 

 of the collar, immediately behind the ring of ten- 

 tacles ; c.r, ciliated ring ; d, diverticulum (paired) of 

 alimentary canal ; HI, mouth ; n.s, central nervous 

 system ; p, nerve running round the ventral border 

 of the proboscis ; s, sense-organ ; s.s, subneural 

 sinus, a vascular space whose hind wall is con- 

 stituted by the front boundary of b.c 2 , its front 

 wall being formed by the hind wall of b.c 1 ; in this 

 region is seen a median outgrowth of the alimentary 

 canal, which may be compared with the notochord 

 of Ceplmlodiscus, or of the young Tornaria (cf. 

 Morgan, J. Alorphol. v. 1891, Plate xxvi. Fig. 40.) 

 (After Masterman.) 



space. It appears, however, from the account given by Ikeda, 

 and followed by Goodrich, that the old Actinotrocha has two 

 distinct spaces in front of the septum. The first of these corre- 

 sponds with b.c 1 + most of &.c 2 in Fig. 14, and is continuous 

 with the cavities of the larval tentacles. Into it project the 

 blind ends of the larval excretory organs, which, according to 

 Goodrich, bear numerous " solenocytes " similar to those described 

 by the same author in Amphioxus and in Polychaet worms (Fig. 

 79, p. 127). The second cavity is a relatively small crescent 

 (not shown in Fig. 14), lying on the anterior face of the septum, 



1 J. Coll. Japan, xiii. Pt. iv. 1901, p. 507. 



Arch. Biol. xviii. 1902, p. 495 ; Wiss. Mceresuntersuch. vi. Abt. Helgoland, 

 Heft 1, 1903. 



3 Quart. J. Micr. Sci. xlvii. Pt. i, 1903, p. 103. 



4 Zeitschr. wiss. Zool. Ixxv. 1903, pp. 391, 473. 



