300 GENERAL HISTORY OF THE INFUSORIA. 



family of Polypes, and ** which is probably to be referred to the Acinetina. . . . 

 In the oval embryos, ciliated on one side, which were squeezed out of the body 

 of the mother, we were enabled to convince oiu^selves that these coi-puscles 

 were enclosed, from two to nine together, in a roundish proper vesicle " (cell). 



Muscles. — Ehrenberg presumed the existence of internal muscles, to ex- 

 plain the varied and active movements of the Ciliata, — a presumption required 

 by his hypothesis of the repetition of the organization of higher animals in all 

 lower forms, but entirely unwarranted by analogy. Dujardin considered the 

 whole bulk of the body to be composed of ' sarcode,' having an inherent con- 

 tractility, and the som^ce of all the movements. Little doubt can exist that 

 the cortical lamina is the seat of contractility, — not that it is muscular on this 

 account, but that, as animal tissue in its simplest condition, it possesses the 

 pro]3erty of contractility as one of the characteristics of such tissue, along 

 with others, such as sensibility, all which, in highly-organized animals, have 

 severally their special structure elaborated for their more complete operation 

 and independent action. In short, in the language of physiologists, the 

 tissues in more perfect animals are differentiated, in the lowest are not so. 



This physiological fact being admitted, the existence of nerve-fibres and of 

 nervous centres, or ganglions, can be no more than imaginary. The same 

 follows of the supposed organ of sense, the so-called eye of Glenodinmm, 

 which many have concluded to be homologous with the coloui'ed specks of 

 Protozoa, of Euglena, and the like. Lieberkiihn's observations would lead, 

 however, to the conclusion that the eye-speck of Ophryoylena rightly deserved 

 that epithet, and is something more than a pigment-spot. His account of it 

 runs thus {A. N. H. 1856, xviii. p. 321) : — " Close by the oral slit, on its 

 concave side, lies the pigment-spot. Its form is extremely irregular, some- 

 times globular, sometimes ellipsoidal, in many cases toothed. Ordinarily it 

 is so distinct as to be at once perceived ; sometimes, however, it is so small 

 that it can only be detected by close examination. In animalcules filled mth 

 strongly-refracting substances alone, it is always difficult to discover it. The 

 pigment-spot of Ophryoglena atra has, on the whole, more unifonnity of form 

 and magnitude. If we squeeze do"\vn an Opliryoglena flavicans between the 

 covering glass and the slider, we find that the pigment-spot is composed of a 

 heap of minute, scarcely measurable granules, strongly refracting hght. I 

 never could discover a lens in the pigment. All the specimens examined by 

 me possessed but a single pigment- spot. Beside this lies always a hitherto 

 unobserved structure, the form of which is perfectly described when we call it 

 a -watch-glass on a small scale. This w^atch-glass-hke organ is transparent 

 and colouiless, and shows no trace of fibrous or any other structure. The 

 cii'cular base has a diameter of about y-g^jth of a millimetre ; its depth 

 amounts to about a thii'd part of this diameter ; the convexity is veiy con- 

 siderable. The watch-glass-shaped organ usually turns its convex side 

 towards the pigment-spot ; its concave side is directed towards the point of 

 the head ; it does not seem to be moveable by the animalcule. When isolated, 

 it withstands the action of water for a longer time than is usually the case 

 with the other parts of the body of this Infusorium. After Ijing some time 

 in water, it swells up in some degree, and frequently becomes perforated by 

 a hole in the middle. The presence of the w^atch-glass-shaped organ is not 

 dependent on the presence of a pigment-spot ; for Ophryoglena atra possesses 

 a pigment-spot, but no watch-glass-shaped organ, while Bursaria flava has 

 a watch-glass-shaped organ, but no pigment-spot. In other Infusoria with 

 eye-spots, as in the Euglenm and Peridinic^a, I have sought in vain for this 

 organ. I have not met with any facts throwing light on its function." 



Notwithstanding-, in the interior of the Ciliated Protozoa there is not an 



