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XXn. — On the Volvox Globator, J% William Cra\vford 

 Williamson, Professor of Natural History in Owens 

 College^ Manchester, 



Eead May 27, 1851. 



From the long period that has elapsed since observers first 

 became interested in the Volvox globator as a microscopic 

 object, it is a matter of some surprise that its structure 

 should still be so imperfectly understood. Such, however, 

 is really the fact. The idea of its unity as an individual 

 animal having been rejected by Professor Ehrenberg, many 

 naturalists adopted the more novel interpretation of its his- 

 tory, enunciated by the illustrious Prussian, who was almost 

 universally considered to have dispelled the obscurity with 

 which this elegant organism was previously invested. 

 Whilst all honour is acknowledged to be due to this great 

 observer for the brilliant results of many of his labours, it 

 has become manifest, that in points relating to the internal 

 structure and physiology of some of the objects which he 

 has investigated, his conclusions require to be received with 

 a degree of caution. It is now known that he has included 

 in his great work on infusorial animals, a large number of 

 plants, to which he has assigned organs and functions 

 which are really confined to animal life. 



The consequence has been, that doubts have gradually 

 suggested themselves as to how far his conclusions are to 

 be relied upon, in reference to many of the other objects 

 delineated in his magnificent volume. The Volvox globator 

 has come in for a share of this scepticism, and not without 

 reason. But whilst many have disputed the accuracy of 

 Ehrenberg's interpretation of its structure and history, I 



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