302 THE SCHOOL OF Rl^AUMUR 



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explanations which do him no credit. He observed for 

 example in his Plumatella the bodies which are now 

 called statohlasts, a peculiar kind of gemmules. These 

 must, he thinks, be seeds which had been taken in as 

 food. He persuaded himself that they were the seeds of 

 duckweed, and supported the identification by a figure 

 which is totally fallacious. Since his supposed seeds of 

 duckweed were found lying loose in the body-cavity, he 

 concluded that Trembley s description of a continuous 

 alimentary canal, which has been confirmed by all 

 modern observers, must be wrong. 



The " History of the Freshwater Polyps " contains an 

 account of Nais, to which several plates are devoted. 

 We can recognise Stylaria proboscidea,^ Nais serpentina,^ 

 and two others.^ JM 



Seven plates are occupied with Stentor, Vorticella, 

 Carchesium, and other ciliate Infusoria. Leeuwenhoek ^ 

 had discovered these things long before ; Trembley, ^ 

 Baker, Schaefier, and Brady had called them polyps, and 

 placed them next to Hydra. Roesel gives much better 

 figures than his predecessors. The history of the Polyps 

 ends with Volvox (which had been already described 

 by Leeuwenhoek and Baker) and a minute, colourless 

 animalcule, which is named the lesser Proteus, because 

 Eoesel took it to be a smaller species of Baker's Proteus.* 

 He gives many careful figures of this, and shows that it 

 frequently changes its shape, that its granular contents 

 are enclosed by a firmer external layer, and that it 

 occasionally divides spontaneously into two. If he had 

 recognised the nucleus and the contractile vacuole, his 

 account would have been fairly complete. This is the 



1 PI. 78, Figs. 15-18 ; pi. 79, fig. 1. ^ pi. 92. 3 pi. 93, 



* Baker's Proteus was a ciliate Inf usorian. Employment for the Microscope, 

 ch. v., pi. X, fig. 11. 



