F. STEIN, 1859. R. M. DIES ING, 1848-1866. 25 



tion of the higher or Ciliate section of the Infusoria first introduced by him a 

 few years previously,* and which has since been generally adopted as the 

 most natura 1 and convenient scheme yet proposed. In accordance with 

 this, the ciliate animalcules were divided, with reference to the character 

 and distribution of their cilia, into the four subordinate orders of the 

 Holotricha, Heterotricha, Hypotricha, and Peritricha ; this special volume, in 

 addition to including a complete summary of the biography and organiza- 

 tion of the Infusoria as known up to that date, constituting an exhaustive 

 account or monograph of the Hypotrichous section. The position conceded 

 to the Infusoria by Stein in this treatise is that of the highest group of the 

 Protozoa, though, taken individually, a more complex type of organization 

 is assigned to them than is involved with the unicellular interpre- 

 tation of Von Siebold. The characteristic contractile vesicle, with its 

 frequently associated radiating canals, more particularly, is here accepted 

 as formerly by O. Schmidt and Claparede and Lachmann as indicative 

 of a more or less remote relationship with the Turbellaria and lower 

 Annelids. 



The interval intervening before the issue, in the year 1867, of Stein's 

 second volume of his 'General History of the Infusoria,' bore substantial fruit 

 through the researches of Balbiani and T. W. Engelmann in the direction 

 of that more extended knowledge of the developmental phenomena of the 

 class referred to at length in a succeeding chapter. The number of known 

 infusorial forms was also considerably enriched, and their structure accu- 

 rately described and delineated by the authority last quoted and many 

 other able investigators, among whom the names of A. Quennerstedt, 

 H. J. Carter, Frederick Cohn, J. D'Udekem, and A. Wrzesniowski, are 

 especially conspicuous. 



In association with the period now under consideration the novel 

 interpretation of the affinities of the Infusoria and proposed subdivision of 

 the group introduced by R. M. Diesing, may be suitably referred to. In 

 accordance with the views of this author, the sub-kingdom of the Protozoa, 

 as instituted by Von Siebold, possessed no real existence, the entire assem- 

 blage of forms included in it representing simply lower or imperfectly 

 developed conditions of various more highly organized animal groups. The 

 Rhizopoda and Foraminifera were thus held by Diesing, following the views 

 of D'Orbigny, to be degraded headless Mollusca, the majority of the Ciliata 

 and mouth-bearing Flagellata to be lower worms, while the Vorticellidae 

 and Stentors, with reference to the closely approximated location of 

 their oral and anal apertures, were referred to the Polyzoa, and collected 

 into a group upon which he conferred the title of the Bryozoa Anopisthia. 

 This breaking up of the class of the Infusoria and distribution of its 

 members among various other Invertebrate sub-kingdoms, while first 

 proposed by Diesing in the year 1848, received its full development in 

 his ' Systema Helminthum, Order Prothelmintha/ and ' Revision der 



* ' Sitzung. der konigl. Bohmischen Gesellschaft der Wissenschaften,' Oct. 1857. 



