136 DESCRIPTION OF [Polygastrica. 



Spirillum. Spiral consists of one and half tarns ; fibres 

 short, stout, and much bent ; articulations distinct ; 

 colourless ; when dry, the articulations are more distinct. 

 Ehrenberg remarks, that the form of this species is like 

 a bow; and Miiller, that it resembles the letter V. Fig. 61 

 represents a group magnified 800 diameters ; that with 

 dotted lines indicates the impression left on the eye 

 when the creature is in motion. Found in stagnant water 

 having a mildewy scent. Length about 1 -1 500th. Thick- 

 ness 1- 20000th. 



101. SPIRILLUM volutans ( Vibrio spirillum, M.) The 

 twirling Spirillum or screw Vibrio. Consists of three, four, 

 or more coils ; fibres very tortuous, long, and stout ; arti- 

 culations distinct ; colourless. Found in vegetable infu- 

 sions. Length of spiral 1 -2200th to 1- 500th. Thick- 

 ness 1- 14400th. 



This creature strongly resembles the minute Algae dis- 

 covered by Mr. Thompson, as producing the various 

 colours which the Ballydrian Lake assumes, and which he 

 has described under the name of Anabaina spiralis, in 

 vol. v. of the Ann. Nat. Hist. ; his figures resemble 

 group 61. The genus is characterized as if consisting of 

 extremely minute moniliform thread, of a rich green 

 colour, and regularly spiral, like a corkscrew ; globules of 

 equal size throughout." In decomposing, it changes first 

 to blue and then ferruginous; each globule appeared to 

 consist of a number of granules enveloped in a hyaline 

 membrane. Length of a single coil about l-200th. 



102. SPIRILLUM bryozoon. The moss Spirillum. Coils 

 consist of a thick body, with a delicate wavy hair-like 

 proboscis. These creatures, found in the reproductive 



