NOTES ON THE ANATOMY OF DINOPHILUS. 41 



As in other species of Dinophilus, salivary glands open into the 

 anterior division of the CESophagus. 



The stomach (which, during life, is of a rich orange colour) is 

 ciliated throughout : it ends csecally on the dorsal side of the com- 

 mencement of the intestine, as in D. gigas. 



The intestine, like the rest of the alimentary canal, is ciliated. 

 It opens into the stomach by a narrow aperture situated on the ven- 

 tral side of the latter. 



As will be seen by reference to fig. 1, the oesophagus and its 

 muscular appendage belong to the first segment of the body, the 

 stomach occupying the second, third, and fourth segments, whilst the 

 intestine is found in the fifth and posterior part of the fourth segment. 



Nervous System — Although Korschelt (6) and Repiachoff (12) suc- 

 ceeded in finding the brain of D. gyrociliatus, our knowledge of the 

 nervous system of Dinophilus is in the main due to Weldon (13), 

 who has not only described the brain, but has shown that this struc- 

 ture is connected with ventral cords, whose arrangement resembles 

 that found in Protodrilus {v. Hatschek, No. 5) . , 



The nervous system of D. tseniatus exhibits a feature which has 

 not hitherto been described in any species of Dinophilus. The 

 ventral cords are distinctly segmented, the number of ganglionic 

 enlargements — five — corresponding with that of the segments of the 

 body. 



The ventral cords (figs. 3, 10 and 11) are situated outside the 

 basement-membrane of the skin, and lie, widely separated from one 

 another, immediately on the median side of the longitudinal muscles 

 (as in D. gigas). The cords seem to be provided with an external 

 investment of ganglion-cells along their whole length. The gan- 

 glionic swellings (fig. 3) appear to be shifted backwards, relatively 

 to the segment to which they respectively belong, so that the middle 

 of the segment on the dorsal side (as indicated by the ciliated rings) 

 is in front of the corresponding ganglion. 



In transverse section (fig. 10) it may be seen that each pair of 

 ganglia is connected by a transverse commissure. I could not 

 satisfy myself of the existence of ganglion-cells in connection with 

 this commissure, although, as the whole ventral nervous system lies 

 in the ectoderm, it is possible that some of the nuclei which are 

 adjacent to the commissures may really belong to ganglion-cells, and 

 not to the epithelial portion of the skin. No transverse commissures 

 were discovered other than those which pass between the ganglia. 



The brain is very large, and fills up nearly the whole of the praeoral 

 lobe (figs. 3, 9). It consists internally of fibres, and externally of 

 numerous ganglion-cells arranged in groups. The structure of the 

 brain is very complicated ; its surface appears lobulated, owing to 



