AC ALE PH. E. 



surface, by the constant currents which they excite, necessarily 

 ensure a continual supply of aerated water, which bathing the 

 whole body exposes every part to the influence of oxygen, and 

 Ehrenberg thinks that he has even perceived the existence of a 

 delicate net-work of minute canals hollowed out in the periphery 

 of some species, which, if filled with nutritive juices, might be 

 regarded as the first rudiments of a vascular system. 



(92.) The nervous matter, or neurine, which we must suppose 

 to exist in a molecular state mixed up with the tissues of the body, 

 has never been detected in an aggregated form ; nevertheless, upon 

 many species, when observed under good glasses, it is easy to see 

 one or two extremely minute red or brown specks, which have 

 been conjectured to be eyes, though probably without further 

 reason for the supposition than the resemblance which they 

 exhibit, in colour at least, to the visual organs of some ento- 

 mostracous Crustacea : in some cases, these points exist only in 

 the young animalcule prior to its birth ; thus in Eudorina 

 elegans, an animal resembling the Volvox in its mode of gene- 

 ration, the offspring, while confined in the body of their parent, 

 are each seen to be furnished with a red speck, as well as a long 

 bristle, which is exserted through the parent envelope ; but as soon 

 as, by the rupture of the sac, the contained gemmules are set at 

 liberty, a time when we should imagine the faculty of vision to be 

 most useful, the red point disappears ; and, were that the only 

 means of appreciating the presence of light, we might suppose the 

 liberated animalcules to be deprived of the power of seeing when 

 most capable of enjoying it. 



CHAPTER V. 



ACALEPHJE, (CuV.) 



(93.) The fourth class of acrite animals is scarcely inferior to 

 that last described, either in numbers or interest. The ocean in 

 every climate swarms with infinite multitudes of animals, which, 

 from their minuteness and transparency, are almost as impercepti- 

 ble to the casual observer as the infusoria themselves ; their exist- 

 ence being only indicated by the phosphorescence of some species, 

 which, being rendered evident on the slightest agitation, illuminates 



