ANALYTICAL INDEX. 



261 



CHAPTER in.— continued. 



Multitude of planulfe from tliein, . . . pagf, 106 



Scum on the surface of the water secreted from the planulse, 107 



Natural position of the hydra, . . . . ib. 



Twelve tentacula acquired in 40 days, . . .109 



None of 2000 hydrae acquired more, ... ib. 



Suitable treatment of living subjects, . . . . ib. 



Medusa is the parent of the Hydra tuba or Strobila, . 110 



§ 3. Medusa bifida, — origin, . . . . . ib. 



Period of its appearance, . . . . . Ill 



Variety of Medusae, . . . . . .112 



Baster observed Medusa bifida in 1761, . . . ib. 



Black specks rather glandular than ocular ? . . .113 



Medusae bifidse are transient, .... ib. 



Survives 55 or 60 days, . . . . . ib. 



Medusa bifida originates from the Hydra tuba, . . 114 



Pendulous roll of Medusa3 forming there is gradually dissolved, . 116 



Basis remaining permanent becomes a hydra, . . 117 



Period occupied in dissolution, .... ib. 



Old tentacula obliterated, others evolved, . . . 120 



Production of pendulous roll, . . . .122 



How and where is it generated ? . . . . 123 



Obstacles to prosecuting the history of the Medusa, . . 1 24 



Number in the roll, . . . . . 125 



Roll dissolved, basis perfected, . . . .126 



Bulb or basis become a hydra surviving above a year, . 127 

 Monstrosities of the Medusa?, .... 128 



Medusa and hydra of different nature, ... ib. 



Conclusions, . . . . . . .129 



Plates XVIII., XIX., XX., XXI., explained, . 130 



CHAPTER IV.— The Sertclaria, .... 



Zoophyte of comprehensive signification. 



Numerous inorganic combinations with the same animal, 



Nomenclature changed, .... 



Addition of species preferable to midtiplied genera. 



Precipitate nomenclature. 



Animated portion of zoophytes overlooked, 



Dr Johnston corrects this error. 



Analogies of Tubularia and Sertularia, 



134 



ib. 

 135 



ib. 



ib. 

 136 

 137 



ib. 

 13S 



