PARAMECIUM CAUDATUM 



335 



movements are spontaneous, voluntary, and very carefully co-ordinated. As a consequence, the animal can dart 

 about and lash into its mouth by the aid of artificial water-currents any food in its vicinity. 



The movements of paramecium, as seen under the microscope, are at once striking and interesting. The little 

 creature dashes about at great speed without any apparent means of locomotion ; the ciha being so fine as to escape 

 observation when moving quickly. The careering of the paramecium is regulated with the utmost precision ; the 

 little creatures avoiding each other and obstacles of every kind with amazing agihty. The movements of paramecium 

 are unquestionably under control, and must be regarded as voluntary in character, in which respect they resemble 

 the movements in the higher animals. They are not due to a muscular or nervous system, neither of which are 

 present. Neither are they due to irritabiUty or extraneous stimulation or reflex action of any kind. The existence 

 of direct, spontaneous, voluntary, co-ordinated movements in the paramecium, as apart from nerves, muscles, and 

 other differentiated structures, proves conclusively that rudimentary, undifferentiated, living matter contains in the 

 atoms and molecules of its substance, in a potential form, many, if not all, the 

 peculiarities and powers residing in the most highly organised Uving matter. This '^i 



is a subject of great importance, and cannot be too seriously pondered, as it bears 

 directly upon a First Cause, Design, and means to ends. 



The mouth of the paramecium is situated on the side of the body in a cone- 

 shaped depression or sht (vestibule) at the junction of the posterior and middle third 

 of the ventral surface, and in its immediate vicinity is found the imperfect anus. 

 By the mouth the food, generally microscopic algee, enters and is made to gyrate 

 within the body (vide darts) in a manner not unlike that by which the food (chyme) 

 is made to travel round the greater and lesser curvatures of the human stomach. 



The contractile vacuoles, two in number, possess the remarkable centrifugal and 

 centripetal opening and closing movements described in the amoeba. There can be 

 no doubt that these movements are fundamental. This seems proved by the fact 

 that they occur in the most rudimentary and most complex organisms alike. They 

 are connected with the intake and output of extraneous matters, in alimentation, 

 respiration, circulation, secretion, excretion, reproduction, &c. In all animals, be 

 they small or great, simple or complex, provision must be made for the intake, 

 circulation, assimilation, and output of extraneous matter in a gaseous, liquid, or 

 soUd form. Even the simplest cell must be so endowed. 



The nuclei are two in number, namely, a large oval-shaped macro-nucleus and a 

 small micro-nucleus. The nuclei are important from a reproductive point of view. 

 When reproduction takes place the nuclei divide ; the reproductive process being 

 subsequently completed by a union or conjugation of two separate individuals, thought 

 by some to represent male and female elements. 



" During the reproductive process two individuals are in close contact along 

 their ventral surface, their protoplasm becoming continuous through their mouths 

 as follows : — 



" 1. In each individual the macro-nucleus breaks up and disintegrates, to be thrown out or absorbed, and the 

 micro-nucleus grows rapidly, and then divides by two rapid divisions into four, two of these pieces being absorbed. 

 Thus by these processes the macro-nucleus and micro-nucleus are now reduced to two fragments of a micro-nucleus. 

 The fragments are each one-fourth part of the original overgrown micro -nucleus. 



" 2. In each individual one of the parts moves across into the other individual, and fuses with the remaining 

 part of that individual. Sometimes the migrating parts are termed the male pronuclei, and the other two the female 

 pronuclei. 



" 3. Soon after this, communication between the two individuals becomes interrupted, and they part. In the 

 meanwhile the single-fused nucleus in each divides into two and then into four, so that each individual has then four 

 nuclei. 



"4. Two quarters pass to each end of the animal and binary fission takes place. One quarter grows into a 

 macro-nucleus and the other remains a micro -nucleus. The result is a pair of each offspring with a macro-nucleus 

 and a micro-nucleus." ^ 



The process of conjugation by which the reproductive act is completed, and which requires two separate 

 individuals for its consummation, has an obvious connection with reproduction in the higher animals, so that viewed 

 from the three important points of alimentation, locomotion, and reproduction, the paramecium may be said to 

 > "Text-boQk pf Zoology," by Arthur T, Masterman, M,A, (Cantab.), D.Sc, (London and St. Andrews), F.R.S.E. 1901, pp. 91 and 92. 



Fig. 69. — Shows adult specimen of 

 Paramecium, lateral view ; anterior 

 end downwards, x 60. a, mouth ; 

 b, imperfect anus ; c, cilia ; d, 

 trichocyst ; h, thread of same ; e, 

 one of the contracting vacuoles ; 

 /, medulla ; g, cortex ; i, food- 

 vacuole ; j, macro-nucleus ; k, micro- 

 nucleus. The darts indicate the 

 direction in which the food travels 

 during digestion (after Masterman). 



The essential changes are 



