HOTIFERA. 117 



armed could be expelled from the parent animal in the usual 

 way ; we must therefore suppose that the spines grow, or become 

 hardened at least, subsequently to the birth of the ovum. Since the 

 discovery of this microscopic egg in a recent state, similar bodies 

 have been detected in great numbers in a fossil condition im- 

 bedded in flint ; a fact which, in conjunction with what has been 

 already stated ( 74) concerning the occurrence of the shells of 

 loricated infusoria in the same situation, tends materially to show 

 that masses of flint are agglomerations of siliceous particles inclos- 

 ing immense quantities of the debris of organized bodies.* 



That the bryozoa are very far superior to the polyps in 

 all the details of their structure, will now be sufficiently mani- 

 fest. The ciliated tentacula, although selected as affording the 

 most convenient character for the guidance of the Zoologist 

 from the constancy of their coexistence with elaborately or- 

 ganized internal viscera, are probably only organs of secondary 

 importance in a physiological point of view ; for the analogies 

 between this class and that which will form the subject of our 

 next chapter are not to be mistaken, and the transition from one 

 to the other is so gradual, that where observation has failed in com- 

 pletely developing the anatomy of the animals we have been 

 considering, the facts which have been ascertained concerning the 

 Rotiferous Animalcules, will go far towards supplying the defi- 

 ciency. 



CHAPTER IX. 



fRoTiFERA (Ehrenberg). 







(153.) The class of animals that next presents itself for our 

 consideration was, until very recently, confounded with the chaotic 

 assemblage of minute creatures to which the name of Infusorial 

 Animalcules was indiscriminately applied; but the information at 

 present in our possession concerning their internal structure and 

 general economy, while it exhibits, in a striking manner, the assi- 

 duity of modern observers, and the perfection of our means of ex- 

 ploring microscopic subjects, enables us satisfactorily to define the 

 limits of this interesting group of beings, and assign to them the 

 elevated rank in the scale of zoological classification to which, from 

 their superior organization, they are entitled. 



* Tuipin, Ann. des Sciences Nat. 1837. t Rota, a wheel; fcro, / bear. 



