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PROTOZOA OF HERTFORDSniRE. 125 



shaped collar of the Choano-riagcllata. He (Mr. Kent) says that 

 be believes that Stein has misinterpreted this structure. He has 

 examined an extensive series of examples, and he says : "In no 

 instance could any such independent organ be detected, but in 

 place of this it was observed that the anteriorly-developed lip-like 

 prominence occupied a conspicuous position, and might be with 

 ease identified with the looked-for ' collar.' " 



From personal observation I am able to substantiate the correct- 

 ness of Stein's description. Whilst working with Mr. Robinson 

 one evening a short time ago, we fonnd a colony of nine zooids, 

 three of which showed this " collar" most clearly. I could see the 

 peripheral contour as distinctly as possible ; all the others, how- 

 ever, showed only the characteristic lip -like prominence ; after a 

 short time, whilst making a note of the matter, the collar was 

 withdrawn, and the zooids presented the same appearance as the 

 others ; the animalcules were all extremely plastic and changeable 

 in shape, and from this I infer that the so-called "collar" really 

 exists, but can be withdrawn or extended at will. 



There are twelve other families of the Pantostomatous Infusoria, 

 but I have fonnd no representatives, and as our time is short I 

 shall refrain from further remarks upon this section, reserving the 

 remaining families as matter for a fixture paper. 



In conclusion I may mention that the method of illumination 

 which I have employed with most success is that of direct light 

 proceeding through the condenser without the intervention of tlie 

 mirror, and by this means I can make out such delicate structures 

 as flagella and the collar, with a half-inch objective, easily and 

 most distinctly. The powers which I employ are a half-inch and 

 a one-tenth inch objective fitted to a double nose-piece in such a 

 manner that when interchanged for each other they are in focus 

 without further adjustment. For confining the most restless 

 species when under examination I place a little spyrogyra or some 

 other conferva between the cover-glass and slide. 



