Ll>'Ki;A>' SOCIETY OK I,0^'1>0^^ 



Tlie cilia layer occurs in all Ciliata ; it lies immediately bweatk ^^t-j, 

 the cuticle, where this is j)resent, and the whole of the cilia »^i^^/. 

 other mobile appendages are its immediate extensions. Those niust^??-^^- *>. 

 therefore perforate the cuticle or its modifications, when such pro- 

 tective coverings exist. 



The myophan layer is identical with that which most autliors de- 

 scribe as a true muscular layer. It has been demonstrated in most 

 of the Ciliata. It appears as a system of regular parallel fine striae 

 in the walls of the body, and in the Vorticellinae occupies also the 

 axis of the stem, where it forms the characteristic " stem-muscle " 

 of these animals. There can be no doubt that these striae represent 

 contractile fibres, which, by their contraction, effect the various form- 

 changes of the animal. They are thus physiologically analogous to 

 muscles. From a morphological point of view, however, we must 

 regard them as only differentiated protoplasm-filaments. In the 

 morphological conception of true muscle its cell-nature is absolutely 

 indispensable. The so-called muscle-fibrils of the Infusoria never 

 show a trace of nucleus. They can be viewed only as parts of a 

 cell due to the differentiation of the sarcode-molecules of its proto- 

 plasm ; and as they are thus only sarcode lines, Haeckel designates 

 them by the term "myophan," as indicating a distinction from 

 proper muscle. 



The trichocyst layer occurs also in many Infusoria, but not in all. 

 It is a thin stratum of the exoplasm lying immediately on the endo- 

 plasm, and including in certain species the trichocysts. The pre- 

 sence of these bodies, which possess a striking resemblance to the 

 thread-cells of the Ccelenterata, has, as we have already seen, been 

 urged as an argument in favour of the multicellularity of the Infu- 

 soria. But, as Haeckel argues, no evidence of multicellularity can 

 be derived from this fact. The thread-cells of the Ccelenterata are 

 themselves the products of a cell ; and we often find many of them 



The family of the CodonellidEe, based on the genus Codonella, Haeckel, is also 

 provided with a bell-shaped case ; but this, instead of being formed of a siliceous 

 lattice-work, consists of a ehitine-like organic membrane, through which siU- 

 ceous particles are scattered. The family is, however, chiefly characterized by 

 the peculiar form of its peristome. This is funnel-shaped, and provided on its 

 margin *ith a thin collar-like expansion. The free edge of this collar is ser- 

 rated, and each tooth carries a stalked lobe of a piriform shape, regarded bv 

 Haeckel as probably an organ of touch. At some distance behind the circle of 

 piriform lobes is situated a ring of long, strong, whip-Uke cilia, which form 

 powerful swimming-organs. The three species dos/ribod are distinguished bv 

 the form of their chiliuous cases. 



