352 ANIMAL BIOLOGY. [Part II. 



endoplast (end.), associated with which , N applied to one side, is a 

 smaller endoplastule, homologous with the nucleolus. There 

 are two contractile vesicles (c. v.), which, at the moment of 

 systole, are seen under certain conditions to become starlike, 

 as if there proceeded from them radiating canals, which thus 

 for a moment became distended. The vestibule (vs.) is a ciliated 

 funnel on the ventral surface. The process of feeding, giving 

 rise to food-vacuoles (/. v.), is similar to that in vorticella. 

 The indigestible residue is passed out by a potential anus 

 (p. a.) or weak spot in the protoplasm of the ventral surface. 



The movements of paramcecium through the water show a 

 curious combination of backward or forward motion and 

 rotation. Interesting observations have been made on the effect 

 of a rise of temperature on these animalcules. It was found 

 that the pulsation of the contractile vesicle grew more rapid 

 until a maximum was reached of 30 C. Beyond this point the 

 pulsations grew less frequent, but the ciliary activity continued 

 to increase up to 35 C., when the co-ordination of the move- 

 ments of the cilia became imperfect, resulting in a peculiar aim- 

 less combination of direct and rotatory motions. At 40 C. the 

 direct movements ceased, while rotation continued to 42- 45, 

 when death ensued. 



Paramcecium multiplies by fission, which is transverse. Con- 

 jugation also takes place, but diifers from that observed in vorti- 

 cella by being transient and not permanent. Two paramoecia 

 become locked together by the close application or union of 

 their oral surfaces. In this condition they may remain for five 

 or six days. During or subsequent to this process the endoplas- 

 tule becomes fusiform and striated, and the endoplast turgid 

 and enlarged. It would seem that the endoplast breaks up into 

 a number of spheroidal bodies, which are ultimately cast out of 

 the body, and not improbably constitute reproductive germs 

 from which daughter paramoecia take their origin. 



Many of the ciliated infusoria are parasites or messmates. 

 In the rectum of the frog, for instance, examples of Balantidium 

 and Nydotherus (Fig. 102, G.) are almost sure to be found. 

 The former has several contractile vesicles, the latter generally 



