64 NATURAL HISTORY 



I observed others having three, four, or five round spots, 

 I began to think myself mistaken ; and should rather 

 suppose them concrete bodies, similar to the pearls in se- 

 veral kinds of shell-fish, did not the regularity of their 

 position render this likewise improbable." 



95. Vibrio paxillifer. The stick Vibrio. Group 43. — 

 This animalcule, or rather congeries of animalcules, for 

 they are mostly attached together in different forms, when 

 magnified appear like pieces of straw of a pale yellow 

 colour, with the inside of an orange brown. They are 

 nearly round, and, if attentively watched, may be seen 

 occasionally to turn upon their longer axis, when a longi- 

 tudinal line may be observed; this is, probably, the 

 hinge or opening of their shell. They vary in length 

 from 1-lOOth to 1 -500th of an inch, and their diameter 

 is from l-20th to 1-lOOth of their length : they require 

 considerable magnifying powder, and large angular 

 aperture, to distinguish their structure. Muller has no 

 doubt included several distinct species under this name. 

 (See Bacillaria.) I find, on reference to my notes, 

 made at different times, that it was not until after I had 

 examined them repeatedly I became satisfied of their 

 animal vitality. They generally reside at the bottom of 

 ponds, but after rain are met with near the surface, 

 giving the water a green tint ; in such cases they are 

 found separate, the agitation of the water having broken 

 the clusters. 



The hair-like animalcule of Baker is nearly allied to 



