218 BENEDEN ON STRUCTURE OF GREGARIN^. 



in the cell by the transformation of the protoplasm into 

 cuticular, muscular, cortical, and medullary substance. 



An important question of which, before concluding, I 

 wish to speak, is the question of the affinity between Gre- 

 garinfe and Infusoria, or rather between Infusoria and the 

 cell. The opinion that Infusoria should be considered as 

 monocellular beings was generally given up the day the 

 »;omplex structure of these organisms became known. That 

 complication appeared to contradict the monocellular nature, 

 for the cell appeared to be the final expression of organic 

 simplicity. Nevertheless it has been impossible until now 

 that statements have been based on the anatomical study of 

 these organisms, or that what one knows of their development, 

 can have been taken into consideration in the attempt to 

 show their pluricellularity. 



All that we have said and made known on the structure of 

 Gregarinae shows, first, that, contrary to the generally re- 

 ceived opinion, a monocellular organism can attain a high 

 degree of complication ; second, that there is a great analogy 

 between the tunics of which our Gregarine is composed and 

 those recognised in Infusoria. We have no reason there- 

 fore, at any rate in consequence of their rather high orga- 

 nization, to sustain a priori that microscopic animals are 

 pluricellular beings ; and it is a question if the muscular 

 layer, the cortical parenchyma, and the medullary substance 

 of Infusoria are not homologous with these same elements in 

 the Gregarinse ; the solution of this question in the affirmative 

 would demonstrate the unicellularity of Infusoria. Without 

 wishing to maintain that these organisms are of a mono- 

 cellular nature, I think we may ask ourselves the question, 

 for our present knowledge of Infusoria has not solved it as 

 yet. The exact knowledge of the autogenic development of 

 these organisms could alone decide the question of the homo- 

 logy of their layers with those of our Gregarina, and throw 

 light on the genealogic affinity which binds Infusoria to the 

 most simjile monocellular organisms. 



