Dr. C. F. J. Lachmann on the Organization of Infusoria. 125 



as possible, we can certainly not consider the Infusoria as such, 

 at least not those which are most accessible to observation, 

 namely, the larger forms, especially Ehrenberg's Enterodela ; the 

 smaller species, which are more difficult to observe, must then 

 be judged by analogy, until we understand better how to observe 

 them. Even if we do not hesitate on account of the remarkable 

 position of the nucleolus outside the nucleus in many Infusoria, 

 the presence of an oral aperture, or, as we shall hereafter show 

 to be the case in the Acinetina, of many mouths, of an oesophagus, 

 and of a second orifice, the anus* (the existence of which we 

 shall prove), there is still a great deal that can be urged against 

 the cell-theory, for which we are particularly indebted to Cohn's 

 observations. 



Cohn showedf that in the Ciliata, besides the thin skin of the 

 body which bears the cilia, or the cell-membrane according to 

 previous views, two other strata are distinguishable in the body, 

 — the inner rotating layer, and a quiescent '^ cortical layer J,'^ 

 often of considerable thickness, surrounding this ; he considers 

 this cortical layer as the cell-membrane, which is enveloped ex- 

 ternally by a ciliated cuticula, and only regards the internal, fre- 

 quently rotating layer as the cell-contents. 



The cuticle, which in plants is generally regarded as a 

 hardened cell-secretion, is then said, in those Infusoria which 

 are ciliated all round, to bear small, four-sided prisms, at the 

 apex of each of which there is a cilium ; these are generally 

 arranged in spiral series, crossing each other §. The supposed 

 cell-membrane or cortical layer encloses the contractile vesicle 

 and a system of vessels proceeding from this (see further on) ; 

 it also frequently contains chlorophyll-globules, or colourless 

 globules of the same form, which were regarded as eggs by 

 Ehrenberg, but as to the signification of which we have as yet 

 no observations. In many Infusoria, especially the Ophryoglencn 

 (in which it lasts long after the decomposition of the animal) and 

 (less persistent) in many species of Paramecium {P. Bursaria, 



* The idea of the cell would certainly by this means be remarkably 

 modified, and by its too great extension would lose all signification. 



t Siebold und Kolliker's Zeitschrift, iii. p. 257, v. p. 420. 



X These are very well seen in Infusoria treated with chromic acid. 



§ In Stentor polymorphus (to which -S. Mulleri and Roeselii are also to 

 be referred) single long hairs stand between these, similar to the hairs of 

 many Turbellaria (fig. 9) ; this is also the case in a species of Infusorium 

 allied to the Stentors, which will be hereafter described. The foot-like 

 hooks {uncini) and styles {styli) articulated to the body, occurring in the 

 Oxytrichinee and Euplotes (and the Aspidiscince of Ehrenberg) are well 

 known : a portion of the former, those which are trailed along, are split up 

 at the apex into as many as eight parts in various Euplotes (for instance, 

 E. patella) ; one of the styles in E. patella bears a number of small lateral 

 branches. 



