Natural History of the Vorticellge. 201 



by Lieberkiihn* upon the same subject will be referred to 

 hereafter in the closer consideration of this striation and its 

 interpretation as muscles. 



In the first place, however, we must turn once more to the 

 above-described transverse striation in the skin of the 

 Vorticellge. 



In the further exposition of his views, Stein applies the 

 interpretation of the body-stria as muscles also to the cu- 

 taneous striae of the Vorticellse, under which he comprehends, 

 as his whole description shows, the above-mentioned more or 

 less regular, fine, transverse striation. He says it is an " appa- 

 rent transverse annulation ; in reality it has a spiral arrange- 

 ment." Moreover, if I have rightly understood the statements 

 relating to it, the outer skin is not the real bearer of these 

 striae, but they are covered by the former, the so-called 

 cuticula. This cuticula fulfils, with regard to the body or 

 muscular striae lying beneath it, the part of a sarcolemma, but 

 envelopes them only in part — that is to say, chiefly externally 

 and (in the longitudinal striae) to the right and left, whilst 

 within they are coherent with the internal sarcode of the 

 body. 



As regards the present admission by Stein of a special mus- 

 cular system in the Infusoria, we can only welcome it as an 

 essential step in advance. It seems to me that, even without 

 the provisional morphological evidence, it must have been as- 

 sumed, a priori, that the sudden, jerking, and convulsive 

 movements such as we see in many Infusoria (for example, in 

 Spirostomiim, Stentor, and the Vorticellae) could not be effected 

 by mere formless sarcode, but only by already differentiated 

 contractile structures — in other words, by muscular elements. 

 Where, in those organisms in which the movements are 

 effected only by the contractions of the formless protoplasm 

 (therefore in the Rhizopoda and creatures like the Rhizopoda), 

 do we find the sudden and convulsive movements of the 

 Infusoria? In all these forms, whether they are indepen- 

 dent or only represent states of development, the movements 

 always appear rather in the form of a slow, uniform, and 

 gradual flowing and creeping, the so-called amoeboid move- 

 ments. Although, therefore, in general the assumption of 

 separate muscular elements in the Infusoria appears to be 

 perfectly justified, we cannot in the special case declare our 

 agreement with the intei-pretations which Stein now puts 

 forward for the body-muscles of the Stentors, Spirostomes, &c., 

 as also for the Vorticellae. 



* Arch, fiir Aiiat. &c. 1857, p. 403, note. 



