THE MEROTOMY OF CILIATED INFUSORIANS. 395 



4. — The rapid regeneration oi D.anser contrasts very remarkably 

 with the slowness of the same phenomenon as exhibited in Loxodes 

 rostrujii (a poli-nuclear species). The fragments take as long as 

 four or five days to regenerate into complete individuals as before, 

 but the author is unable to demonstrate that the speed of regen- 

 eration bears any close relationship with the mono- or poli-nuclear 

 states. 



5. — Sometimes, in the course of regeneration of the fragments 

 of Loxodes, a small secondary merozoite, containing one, or per- 

 haps several, nuclei, will form at the expense of the principal 

 merozoite, and in time become free. 



6. — Fabrea salvia (a ciliate of the salt or brackish swamps) 

 regenerates like the fresh-water species. Those fragments which 

 contain no nucleus will probably live for eight or ten days, owing 

 perhaps to the unusual vitality of this species. 



B. — The author's researches on Paramcecium aitrelia, P. Bursa- 

 ria, and Colpidiwn, show that — 



I. — ParamcBcium aurelia constitutes an exception with respect 

 to the property of regeneration depending on the nucleus. The 

 mutilated individual will live for a month or more without showing 

 any signs of regeneration. 



2. — Only the contractile vesicles regenerate, but their regenera- 

 tion does not constitute a new organic formation. 



3. — When the loss of substance is small, as, for example, a 

 small portion of any extremity of the body, reproduction will only 

 be effected in a series of subsequent generations produced by 

 fission, provided the merozoite lives under most favourable circum- 

 stances. In these conditions the regeneration of the posterior 

 pole takes place more rapidly and completely than that of the 

 anterior pole. 



4. — Fragments which contain no nucleus regenerate to a much 

 less extent than others containing a nucleus, and disappear more 

 readily in the cultures. 



5. — When fragments without a nucleus are stained with sulpho- 

 alyzarin-violet, the colour does not change into red or orange in 

 the vacuoles, thus proving the absence of acid. The acid secretion 

 of the vacuoles, and probably also that of other digestive juices, 

 appears to depend upon the nucleus. 



