210 THE PROTOZOA 



described may be phenomena of agglomeration associated with a similar 

 condition. 



In Radiolaria, Borgert\152) describes fatty degeneration affecting the 

 nucleus as well as the protoplasm, both endoplasm and ectoplasm. The 

 nucleus becomes converted entirely into a vesicle filled with a mass of fat- 

 globules, or into a number of such vesicles. 



In Tocophrya quadripartita subjected to starvation, after the refringent 

 bodies (p. 458) have been absorbed, the nucleus becomes modified in structure, 

 the tentacles are retracted, active budding takes place, and with the last bud 

 formed the nucleus disappears and the remaining protoplasm dies away. 



From a consideration of the various examples of degeneration 

 from different causes, it appears that the first part to be affected 

 is always the nucleus, and that the other derangements of the 

 structure and functions of the body are secondary consequences 

 of an abnormal condition of the nucleus. 



The regeneration of lost parts of the cell-body of Protozoa has 

 been the subject of experiment by a great number of investigators. 

 The methods employed have consisted mainly in mutilating the 

 body or cutting it up in o a number of pieces, in order to find out 

 to what extent the fragments possess the power of regenerating the 

 lost parts. The experiments have led to one very definite result, 

 which can be expressed briefly : no separate part of the body is 

 capable of continuing its vital activities indefinitely, or of regenera- 

 ting any of the deficiencies in the structure of the body, if it does 

 not contain the nucleus or a portion of the nucleus. Non-nucleated 

 fragments may continue to live for a certain time ; in the case of 

 amoeba such fragments may emit pseudopodia, the contractile 

 vacuole continues to pulsate, and acts of ingestion^ or digestion 

 of food that have begun may continue ; but the power of initiating 

 the capture and digestion of food ceases, consequently, all growth 

 is at an end, and sooner or later all non-nucleate fragments or 

 enucleated bodies die off. A Polystomella which possesses a nucleus 

 can repair breakages to the shell ; an individual deprived of its 

 nucleus cannot do so (Verworn). On the other hand, an isolated 

 nucleus, deprived of all protoplasm, dies off ; but a small quantity 

 of protoplasm containing the nucleus or a part of it is able in some 

 cases to regenerate the whole body, and to produce a complete 

 individual of small size. 



In experiments on regeneration the Ciliata are the objects of choice ; their 

 complicated structure permits the regeneration that has taken place to be 

 estimated accurately ; their size renders the mutilation more easy to perform ; 

 and the large size and frequently extended form of the nucleus makes it 

 possible to divide up this body also. In recent experiments Lewin (171) 

 has succeeded in dividing Paramecium into a number of fragments (" mero- 

 zoa "), containing each a portion of the macronucleus. Only one of the 

 merozoa obtained in this manner contains the micronucleus, which is too 

 minute to be divided by a mechanical operation. Except when the Paramecium 

 was in process of division, only one merozoon recovered the normal body- 

 form and proceeded to divide ; and the interesting result was obtained that 



