368 



EUNICEA LABIDOGNATHA NUDA. 



Minor injuries to the first segment are rapidly 



are removed no regeneration ensues, 

 repaired. 



Another experiment was made by Braem, 1 who halved a female example with ripe 

 eggs. The anterior region with the head and thirteen segments regenerated seven 

 segments in three weeks. Moreover, the female elements had disappeared, and were 

 replaced by male. The author thought that in consequence of the injury the indifferent 

 germ-cells had developed into male cells. 



EUNICEA LABIDOGNATHA NUDA. 



Both halves of the jaws have an equal number of pieces. No true cephalic tentacles. 

 Some with and some without branchiae. 



The body-wall in the Lumbrinereidse (Fig. 75) is characterized by the toughness and 

 iridescence of the cuticle, the comparative thinness of the hypoclerm and the circular layer, 



Fig. 77. — Transverse section through the body-wall of Lumbriconereis fragilis. The massive condition of the 

 dorsal and ventral longitudinal muscles is apparent. The oblique muscles are attached above the 

 nerve-cords. 



and the massiveness of the dorsal and ventral longitudinal muscles, which occupy the 

 greater part of the area in transverse section. Moreover, the marked dissimilarity which 

 usually distinguishes the dorsal from the ventral longitudinal muscles is in this group not 

 apparent. Both form compact masses of fibres, slightly diminished towards the middle line 

 clorsally and ventrally. The ventral muscles form the thickest and shortest masses, 

 though, as mentioned, the usual disproportion is not pronounced. In consequence of the 

 great development of the ventral muscles the nerve-cords are pushed inward, their con- 

 nection with the superficial parts being by a pedicle. As a rule a conspicuous neural 

 canal occurs superiorly, and it is often as large as the great ventral vessel above it. To 

 the dorsal edge of the investment above the neural canal the oblique muscles are attached. 

 Fibres from the circular muscular layer seem to pass across the gap at the pedicle. In 

 certain forms, as in Lumbriconereis impatiens, a smaller neural canal exists in each trunk 

 below the larger, and indications of a second (branch) occasionally appears. In some the 



1 ' Anat, Anzeiger/ xxxiii, pp. 19—27, 2 figs., 1908. 



