348 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



EXPLANATION OF PLATE XVL 



All drawings made with the aid of a camera lucida, except figs, i and 13. 



Fig. I. Part of a colony of Myosoma spinosa, gen. nov. The two stolons 

 which are represented were not actually growing side by side, 

 but were chosen to show the variability in segmentation. They 

 are, however, typical. The arrangement of the younger poly- 

 pi des is somewhat diagrammatic, but each individual is as faithful 

 a copy as could be made. X 25. 



Fig. 2. A single polypide of Myosoma spinosa, showing a characteristic 

 position, and the arrangement of the muscle fibers in the stalk. 



X 75- 

 Fig- 3- Para-sagittal section of the same through calyx and part of stalk, to 



show the somatic ventral muscle and its continuity into the stalk. 



X 300. 

 Fig. 4. Frontal section of the same, close to ventral wall of stomach. It 



shows the continuity of the muscle fibers from stalk to calyx, and 



also a few fibers of the branches of the ventral muscle. X 300. 

 Fig. 5. Cross-section of the calyx showing the branches of the somatic 



ventral muscle which form the atrial retractors. Section near the 



base of the oesophagus. X 130. 

 Fig. 6. Same as above (fig. 5), but three sections higher. X 130. 

 Fig. 7. Same as the two preceding figures, the section passing through the 



point where the atrial floor (els. at. fl.) begins to appear. X 130. 

 Fig. 8. Sagittal section of calyx of 31. spinosa, showing the connection of 



muscle fibers with the genital duct. X 650. 

 Fig. 9. Cross-section near the base of three tentacles of the same, to show 



the tentacular muscles. X 300. 

 Fig. 10. Longitudinal section of the same. X 300. 

 Fig. II. Cross-section of the stalk of 3f. spinosa a few sections below the 



calyx, showing greater thickness of the muscle sheath on the 



ventral side. X 130. 

 Fig. 12. Same as the preceding, except that the section passes through the 



lower part of the stalk. X 130. 

 Fig. 13. Part of a colony of Gonypodaria ramosa, sp. nov. X 15. 

 Fig. 14. Part of an old stalk of G. ramosa, the distal end of which shows a 



regenerating polypide. X 100. 

 Fig. 15. A cluster of branches formed at the base of a muscular dilatation 



of the parent stalk. A transition from simple branching such as 



is shown in fig. 13, and stolonic branching is indicated by the 



growth of a second branch [br. 2) from the basal dilatation of the 



first [br. 1). X 100. 

 Fig. 16. Represents a simple branch and a stolonic process growing from 



the base of a muscular dilatation of the parent stalk. X 100. 



