ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
493 
cellular secretions — secretion of the cuticle, of the acid fluid in the food- 
vacuoles, and, perhaps, other digestive fluids; the regeneration or 
reconstitution of organs and of the general form of the body, and the 
ultimate stages of division. There is no antagonism between the proto- 
plasm and the nucleus, but rather there are reciprocal relations whence 
results a harmonious action, which maintains their vitality and assures 
the integrity of their functions. 
Stentor polymorphis and St. igneus were found to be, with regard to 
merotomy, exactly like St. cseruleus ; * that is to say, fragments which 
contained a nucleus were alone capable of regeneration, while fragments 
which had no nucleus were destroyed after a few days. In JDileptus 
anser , where the nuclear substance is dispersed in the form of small 
granulations in all parts of the plasma, all the fragments have some 
power of regeneration, and it is very rapid. This rapid regeneration 
contracts with the slowness of Loxodes rostrum , a species with multiple 
nuclei, the fragments of which require no less than four or five days for 
the reconstitution of complete individuals. In the course of the regenera- 
tion of the fragments of Loxodes , a small secondary merozoite is some- 
times formed spontaneously at the expense of a portion of the principal 
merozoite which contains one or several nuclei ; this portion becomes 
free after being more or less completely organized into a small Loxodes. 
Paramsecium aurelia forms a remarkable exception to the general 
property possessed by Protozoa of regenerating the parts which they 
have lost under the influence of the nucleus. Mutilated individuals may 
live for a month or more without presenting any signs of regeneration. 
The contractile vacuoles are the only parts which are regenerated, but 
this is not an organic new formation. It is only when the loss of 
substance is slight, as when a small part of one of the extremities of the 
body is cut, that it is able to effect repair. Fragments which contain no 
nuclear portion disappear in the cultivations much more rapidly than 
non-regenerated nucleated fragments. Experiments with colouring 
matters show that it is probable that the nucleus has an influence on the 
secretion of acid in the vacuoles, and probably also on that of the other 
digestive juices. It sometimes happens that in multiplication by division 
the products do not become free, but remain united and form a kind of 
colony. During such a multiplication the nuclei may remain connected 
together, and form a large mammillated mass. There is in this case a 
suppression of the later stages of division, due probably to a lesion of 
the nucleus of the merotomized individual ; it is never seen except in 
Paramsecia which have suffered a mutilation of their anterior portion. 
Sometimes lesion is followed by a prolongation of substance in the 
region of the wound. 
Reproduction of Orbitolites.j' — Mr. J. J. Lister, from the examina- 
tion of spirit material, has been able to find that large brood-chambers 
are formed at the margin of the disc during the later stages of growth. 
These are at first lined with a thin layer of protoplasm. At a later stage 
the central region of the disc is found to be empty, and the whole of the 
protoplasm is massed in the brood-chambers in the form of spores. 
* See this Journal, 1892, p. 803. 
f Proc. Cambridge Philosoph. Soc., viii. (1893) pp. 11 and 12. 
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