MEDUSA BIFIDA. 131 



Plate XIX. Hydra tuba, Medusa bifida. 



Fig. 1. Group of hydrse in progressive change adhering to a shell, 

 enlarged. 



2. Natural size and aspect of a different portion. 



3. Aspect of another portion, little exceeding the natural size. 



4. Hydra and rouleau, or cylindrical prolongation, with circular 



indenting, enlarged ; bulb, a ; tentacula, b. 



5. Subject farther advanced, the tentacula at the extremity 



subsisting, but the indenting waved. 



6. Subject still farther advanced : tentacula at the extremity 



obliterated. Another row originating from the bulb. 



7. The same, as seen 48 hours later. 



8. Bulb, a, with a spur' at the base, and the cylinder from the 



disc, which is surrounded by tentacula. 



9. The same farther advanced ; tentacula extending ; Medusa 



greatly expanded ; the lobes clasping towards the pro- 

 boscis, d, which projects outwards. 



10. Specimen with Medusse far advanced. Stumps on the bulb 



subsequently extending as tentacula. 



11. Subject natural size, consisting of a hydra with extend- 



ing tentacula, sustaining several Medusse far advanced. 



12. The same enlarged. 



All the preceding figures, except 2. and 11, are enlarged. 



Plate XX. Hydra tuba, Medusa bifida. 



Fig. 1. Group of Medusse swimming at large ; natural size. 



2. Bulb, or developing hydra, sustaining a waved roU of early 



Medusse, terminated by a complete coronet of tentacula. 



3. The same, having lost the coronet ; another distant coronet, 



or circle, developing from the bulb, which is refining into 

 the form of a hydra, with four spurs issuing from the vici- 

 nity of the base : all as seen 48 hours after fig. 2. 



4. Medusa as swimming at large. 



5. Medusa 40 days old. 



6. Bulb refining into a hydra, with tentacula sustaining a re- 



curved column of Medusse attaining maturity ; natural 

 size. 



