THE CIEPHYREA OF JAPAN. 47 



The longitudinal muscles are incompletely divided into fre- 

 quently anastomosing bundles. Two retractor muscles, the ventral 

 pair (mn), arise slightly behind the middle of the body (Fig. 80 

 PL IV). The sexual organs (so) are situated at a short distance 

 behind the roots of these muscles. The intestine is convoluted 

 into about 15 spirals. The spindle muscle {sm) is fixed to the 

 body-wall at both ends. No fixing muscle and no rectal divert- 

 iculum are present. Peculiar to this species is the fact that the 

 œsophagus {œs) is attached to the retractor muscle at a point so 

 far from the fusing point of the right and left retractors, that it 

 appears to be entirely free from the muscle. The segmental 

 organs {so) are about one-third as long as the body proper ; their 

 posterior halves are free of the mesentery joining them to the 

 body-wall. On the dorsal lip of the internal opening or funnel, 

 there is present a very small sac-like body. Eye-spots cannot 

 be discovered. The filamentous tentacles are probably 10 in 

 number. 



ASPIDOSIPHON SPINALIS, n. sp. 



(Figs. 12, 81-85) 



The animals (Fig. 12) belonging to this new species are of 

 small size, the body proper being generally about 10-\ 5 mm., long 

 (28 mm. in one specimen) and about 3 mm. in breadth. The 

 skin appears smooth, and has a light yellowish l)rown color in 

 the main part of the body proper, but is rough and of a deeper 

 brown on the anal shield and the dorsal side of the introvert. 



