UBRAKY 

 NEW YORK 

 BOTANICAL 



OARDEN 



The Microscope. 



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Vol. VIL DETROIT. JANUARY, 1887. No. 1. 



ORIGINAL COMMUNICATIONS. 



OBSERVATIONS ON CIL^TONOTUS. 



DR. ALFRED C. STOKES, TRENTON, N. J. 



EVEN those who only occasionally make a microscopical examin- 

 . ation of a drop of water from the shadowy depths of a weedy 

 pond, or fi'om the dim shallows of a Lemna-covered pool, must have 

 met with one or more specimens of that group of little animals which 

 Ehrenberg named Chsetonotus, or the bristle-backs. In their favorite 

 habitats they abound almost as numerously as the Infusoria, and 

 althouo^h the various species have much in common, so far aa general 

 contour is concerned, their external ornamentation, or rather their 

 protective coat of mail, is wondrously and beautifully varied in 

 appearance and structure. It is to this external ornamentation then 

 that we are compelled to look for aid in distinguishing the several 

 species common to our fresh waters. 



All the Choetonoti are lithe and graceful little creatures, attract- 

 ive by reason of their symmetrical form, their easy and rapid move- 

 ments, their ornate cuticular appendages, and on account of their 

 bravery and evident ability to take care of themselves. They are all 

 free and rapid swimmers, with rather an irascible and pugnacious 

 disposition. Although the mouth is entirely unarmed, with the 

 exception of the single series of setose cilia encircling it, upon this 

 part the little creatures seem to depend for defence, or as a reminder 

 to colliding or incautious inhabitants of the same water, raising the 

 head and striking repeated and comparatively violent blows, at the 

 same time opening the oesophagus with a characteristic snapping 

 movement This applies to Ch. loricatas especially, but I have seen 



