204 THE MEROTOMY OF CILIATED INFUSORIANS. 



the period of excitation — which is generally of short duration — 

 and when the laws of equilibrium are not too profoundly disturbed, 

 the fragments regain their normal orientation and regularity of 

 movement — behaving, in a word, like ordinary Stentors. 



(4) The most apparent and remarkable phenomenon of 

 merotomy is the rapid and complete regeneration of those mero- 

 zoites which contain the whole or part of a nucleus, a single 

 segment of the nuclear chain being enough to induce regeneration 

 as rapidly and completely as that performed by the entire nucleus. 

 Regeneration is generally completed in about twenty-four hours, 

 varying according to the temperature. 



(5) Should the peristome be removed, it is re-formed by a 

 rudiment which, as in reproduction by division, appears first in 

 that part of the ventral surface to which Schuberg has given the 

 name of the branching zone (Verastelungszone). The new peri- 

 stome is completed by a mouth and an adoral zone, which are also 

 formed as in the process of division. The contractile vesicle is 

 not reproduced as a new organic formation of the plasm, but by a 

 simple local dilatation of the previous excretory system. The 

 reconstitution of the nuclear chain is the last act in the regenera- 

 tion of the merozoite. It takes place by successive divisions of 

 the nuclear particles which the merozoite first contained. The 

 new particles having the same volume as the primitive particles, it 

 results that the nuclein increases at the expense of the plasm. 

 The regeneration of the merozoite is sometimes followed by a ten- 

 dency to multiplication by division ; in other words, to a second 

 reproduction of new parts. But these are soon reabsorbed, and 

 the individual reappears in its original aspect. This phenomenon 

 is probably caused by a superabundant physiological activity 

 of the nucleus induced by the lesion. 



(6) The merozoites which do not contain any part of the 

 nucleus never form a complete individual. They present a short 

 period of excitation, which is manifested in the same way as in 

 those containing a nucleus. When a merozoite without a nucleus 

 contains a mouth or anus, it ingests food or rejects the undigested 

 masses like a normal individual. The nucleus is thus shown to 

 have no influence over the ingestion or rejection of food. Mero- 

 zoites without a nucleus do not survive more than from twenty-four 



