PLATE V. 



Fig. 1. Tip of one of the plumes of the polypide of Cephalodiscus, showing the 

 glandular nature of the enlarged region. The filaments {/) have been turned 

 to the left ; ca, central axis of main stem ; hp, hypoderm. The longitudinal 

 fibres running along the axis are observed to the left as well as over the 

 axis ; x 210. 



Fig. 2. Portion of the middle of a plume with the bases of the filaments ( /), viewed 

 laterally, after the action of a dilute solution of potash. The skeletal axis is 

 observed in the centre of each filament, and as this skeletal axis (sk) widens 

 out at its base, the double outline at each side is well marked ; ca, central 

 axis of main stem, with its longitudinal fibres ; x 350. 



Fig. 3. Transverse section of a young bud on the appearance of the first two lophophoral 

 processes or plumes (Ip) as two rounded bosses composed of tissue resembling 

 hypoderm. The buccal disk (bd) is cut at its anterior region, but the central 

 space (be) of the organ is well developed. The collar space (vc) is com- 

 paratively large at this stage, and lies close beneath the nerve-centre ; x 350. 



Fig. 4. Transverse section of the terminal region of the body-cavity of an older bud 

 than the foregoing, the tip of the alimentary canal {al) being left as a thin 

 plate in the centre, and bound dorsally and ventrally by the median 

 mesentery (ms). The great longitudinal muscle is cut near the commence- 

 ment of the pedicle, and already shows the double ventral curvatures so 

 characteristic of the latter ; bt, basement-tissue ; co, the body-cavity ; x 350. 



Fig. 5. Ovum on its escape from the adult ; ec, egg-capsule ; ov, ovum proper ; st, 

 stalk ; X 90. 



Fig. 6. Outline of another ovum in which the yolk is ovoid, instead of circular as in the 

 former case ; x 90, 



