18 



PEOTOZOA. 



phenomenon, and the smallest undulations upon the surface are indicated 

 by luminous circles. On examining one of the animalcules attentively 

 with the microscope, it is further observable that the light given out is 

 not universally diffused through the substance of its body, but is con- 

 fined to minute luminous points scattered here and there, which make 

 their appearance in rapid succession and as suddenly vanish ; so that 

 evidently there is no special organ to which the luminous appearance 

 can be referred, as in the case of the glow-worm and other phospho- 

 rescent creatures. In size these stars of ocean are almost microscopic, 

 the largest of them not much exceeding the dimensions of a pin's head : 

 but the amazing numbers in which they crowd the billows amply makes 

 up for their minuteness ; at certain seasons, indeed, it may be literally 

 said that every drop of every wave contains one or more individuals 

 belonging to the brilliant host. On taking up at random a flask of sea- 

 water, and allowing the little creatures to accumulate, as they always 

 do when at rest, at the top, it will be seen that their bodies will form a 

 stratum equalling in thickness from one-seventh to one-third part of the 

 entire contents of the vessel. After such demonstration as this, it is 

 easy to comprehend how the entire sea, rendered luminous by the pre- 

 sence of Noctilucae, seems to burn with phosphorescent fire. When 

 the surface is tranquil in some well- sheltered bay, these living gems 

 form a kind of cream of liquid light ; or if a wave disperses their myriads 

 and at the same time calls forth by agitation all their brightness, it is 

 easy to imagine how a flame is thus evoked that spreads for miles, 

 giving at a distance the appearance of a uniform sheet of light, but, 

 when closely examined, resolvable, like the nebulae in the firmament, 

 into constituent stars. 



(41.) AMOZB^:. Yery nearly al- 

 lied to theBhizopods in their organi- 

 zation are certain minute gelatinous 

 beings found in our fresh waters, 

 which have long been puzzles to the 

 microscopist, and a fruitful theme of 

 discussion among naturalists (fig. 7). 



Fig. 7. 



These creatures appear under a good 

 glass as minute patches of transpa- 

 rent jelly, having, under ordinary 

 circumstances, a diameter of from 

 s-j-jj-th to -g-J-g-th of an inch, but re- 

 markable for perpetually changing 

 their form at one time shrinking 

 into the appearance of a little globe, 

 then expanding into a flattened ra- 

 diating disc, and again shooting out processes of their substance in 

 various directions, so as to assume all sorts of shapes with the greatest 



Amoeba, showing the vacuoles in its sarcodic 

 substance, a, 6, c, d, some of the various 

 shapes which it assumes. 



