234 



ROBERT PAYNE BIGELOW ON 



oe. t. oesophageal tube, or canal. 



os. osmium. 



ot. rhopalial concretion (otulitli). 



p. proboscis. 



p p. pillar of the proboscis. 



r c. radial canal. 



rh. rhopalium. 



rh. c. rhopalial canal. 



rh. t. rhopalial tentacle. 



s. stem. 



s e. sensory epithelium. 



sep. septum. 



s f. septal funnel. 



s g. subgenital cavity. 



s in. septal muscle. 



s u. subumbrella. 



t. tentacle. 



v. vesicle. 



za. brownish green cells, symbiotic algae. 



PLATE 31. 



Fig. 1. Portion of the calyx and stem of a scyphistoma with a fully developed bud (ft) attached. A, the outline of the 

 same bud when contracted. 



Fig. 2. Similar to the preceding, except for the formation of a second bud (ft') which bears the older one (ft) upon its 

 apex. 



Fig. 3. The form of the plamila-like bud during the first tw,> days after becoming free. A, B, and C, are the successive 

 changes in shape observed in one specimen during a few minutes. The arrows show the direction in which it swims. 



Fig. 4. Larva of probably the third day. A, lateral aspect; B, oral aspect. 



Fig. 5. A larva of about the same age, 48 hours or over. 



Fig. 6. Another larva of 48 hours or over. 



Fig. 7. Larva of the fourth day.. 



Fig. 8. Free scyphistoma of the fifth day, with rudiments of four tentacles. The arrows show the direction of progres- 

 sion and rotation. 



Fig. 0. A scyphistoma of about the same age, with the rudiments of eight tentacles. 



Fig. 10. Oral aspect of a similar larva, perhaps somewhat younger. 



Fig. 11. A scyphistoma a little mare advanced, probably in, the fifth day. 



Fig. 12. A still more advanced scyphistoma of the fifth day. The four tentacles first formed are much longer than the 

 other four. 



Fig. 13. Scyphistoma of the sixth day, attached, and with eight tentacles. 



Fig. 14. Scyphistoma with rudiments of the second set of eight tentacles. Two tentacles of the first series are bifur- 

 cated. 



Fig. 15. Scyphistoma with sixteen tentacles fully developed, in tile attitude of feeding. 



Fig. 16. Oral aspect of a similar specimen. 



PLATE 32. 



Fig. 17. Scyphistoma showing first traces of rhopalial structure. 



Fig. 18. A small portion of the margin more highly magnified. 



Fig. 19. Scyphistoma at a slightly older stage. 



Fig. 20. Small part of the margin of a similar larva. 



Fig. 21. An early stage in strobilization. 



Fig. 22. A rhopalial tentacle of the same specimen seen from the side. 



Fig. 2.3. An older rhopalial tentacle. 



Fig. 24. Strobila in which the rhopalial tentacles have begun to degenerate. 



