REPORT ON ZOOLOGV. 243 



Nitzsch in 1816, who illustrated the structure of the Cercarice 

 and Bacillarice, and with whom rests the merit of having first 

 ascertained the existence of eyes in several species belonging to 

 the former of these groups. Many other observers have pub- 

 lished descriptions of new species, as well as instituted new ge- 

 nera ; but not having had a sufficiently correct idea of the real 

 organization of these animals, they have in too many instances 

 estahlished their characters upon considerations which are found 

 at the present day to be of no importance whatever. This is 

 particularly the case with many new groups instituted by Bory 

 St. Vincent in the DicL Class, d' Hist. Nat., in 1826. In this 

 work, under the Art. MrcROscopxQUES (which name he substi- 

 tutes for that of Infusoria), he has given a new systematic ar- 

 rangement of all the animals belonging to this class ; but being 

 unfortunately based on the external forms, not only are his 

 genera and species greatly overmultiplied*, but his classifica- 

 tion is entirely artificial, and since the researches of Ehrenberg, 

 become perfectly useless. More important views on this sub- 

 ject were entertained by Professor Baer in a paper published in 

 the 13th volume of the Nov. Act. S^c, Nat. Cur., to which al- 

 lusion has been already made in a former part of this Report. 

 He particularly noticed the great differences which appear in 

 the organization of these animals. Carried away, however, by 

 peculiar notions, which led him to consider them as only the 

 imperfect prototypes of other classes, he was for placing them 

 respectively in these classes, and suppressing that of Ii^usoria 

 altogether. 



Ehrenberg's researches, which form quite an epoch in this 

 department of zoology, were first made known in a memoir read 

 to the Berlin Academy in 1830, and published in the Transac- 

 tions of that body for that year. So many excellent analyses of 

 them have already appeared f, that it is not necessary, neither 

 \^ould it be consistent with the length of this Report, to enter 

 here into any detailed account of them. I shall simply mention 

 some of the chief results at which he has arrived with respect to 

 the structure of these animals, and which he has made the basis 

 of an improved classification of them. The principal feature is 

 the discovery that the Infusoria possess a much more complex 

 organization than naturalists before had any idea of. By sup- 



* The extent to which this has been carried, not only by Bory St. Vincent but 

 by other writers on these animals, may be judged of from a statement by 

 lihrenberg, who observes that Miiller has made of the Vorticella Convallaria 

 twelve species, which form with Lamarck, Schrank, and Bory St. Vincent six 

 genera. 



t See the Edinh. New Phil.Journ. for 1831 and 1833. Also the ^nn. des 

 Set. Nat. for March, &c., of the present year. 



B 2 



