3 7 



The lemnh of the second specimen is 21 mm.; the diameter proximally 1 mm., distally 

 0.25 mm.; the length-index 34. 



From the figures the difference in shape is clearly visible ; the one specimen is short 

 and broad, the other long and thin. This depends of course on the state of contraction and 

 thus the length-index is only of comparative value. 



The animals are considerably thicker at the proximal portion, a fact, due to the strohgly 

 developed liver (L), which is situated more proximally than in Chaetoderma nitidulum. The 

 genital gland however extends far less proximally. A strong incision before the liver indicates 

 the spot, where the retractors of the proximal end attach themselves to the body-wall. The 

 proximal end is round and the mouth somewhat V-shaped. The distal part ends in a little 

 knob. The colour is a pale yellow-brown, but the skin is transparent and permits the dark- 

 coloured liver to show through, the animal being tinted consequently a dark violet. The spicula 

 are distinctly visible and this accounts for the animal's extraordinary gloss. Nothing is perceptible 

 of a dorso-terminal sense-organ. 



The spicula are flat and broad (fig. 183 A), imbricated, with broad bases and somewhat 

 tapered; they are finely striped, the stripes crossing each other and giving the spicula a peculiar 

 design. At the posterior end long thin spicula occur (fig. 182), whilst around the mouth-opening 

 very minute spicula are found, represented in fig. 183 B. Thus the spicula differ in shape from 

 those of the known species of Chaetoderma. The cuticle is traversed throughout by spicula; at 

 the posterior and anterior end the cuticle is thicker and there the spicula stand erect (fig. 184), 

 in the middle region the cuticle is thinner whilst the spicula lie flat (fig. 185). The hypodermis 

 has the thickness of 1 cellular layer, with large nuclei; the vesicular "Riesenzellen" (Wirén) are 

 everywhere perceptible (fig. 184 R). Close behind the mouth-opening the cuticle is very thin; 

 in one of the specimens spicula are entirely wanting there, the sections being at the same time 

 not round but broadened on the ventral side (fig. 190); this peculiarity which is not presented 

 by the other specimen, is most probably a consequence of contraction. 



An extremely smal! dorso-terminal sense-knot is present at a spot, similar to that of 

 Chaetoderma nitidulum. 



Likewise as in Chaetoderma nitidulum the 3 muscular layers of the body-wall can only 

 be indicated in the anterior part, whilst behind the head only the circular muscular layer is 

 found. The 4 muscular regions formed by the longitudinal muscles can only be demonstrated 

 in the posterior part of the body and are only slightly developed; for the rest the longitudinal 

 muscles form 1 continuous layer. The separate muscular bundies of the proximal portion differ 

 from those of Chaetoderma nitidulum. 2 Dorsal and some lateral retractors separate from the 

 longitudinal muscles of the body-wall. The 2 dorsal ones (///) divide each of them into 2 

 smaller bundies, which run proximally and ventrally to the right and left of the pharynx and 

 attach themselves to the ventral body-wall in the anterior portion of the body; the lateral ones 

 (///) take a similar course. Besides these there are ventral muscles (///') which originate in the ventral 

 wall and attach themselves to the ventral body-wall behind the mouth-opening (figs. 189, 190). 



The gill-retractors are entirely different from those of Chaetoderma nitidulum (figs. 196 — 200). 

 First there is a very strong muscle, running parallel to the gills, the fibres of which take a 



