192 SUMMARY OF CURRENT RESEARCHES RELATING TO 



swollen, settled in the wider base of its cup, revolved first rapidly and 

 then slowly, showed disappearance of gullet and contractile vacuole, and 

 after some hours went to pieces completely, leaving only a little mass of 

 protoplasm. The conditions were undoubtedly unnatural, but specimens 

 in all stages of the degenerative process may be found in material taken 

 directly from the sea. 



Behaviour of Micronucleus in Regeneration.* — K. R. Lewin has 

 studied this in Stylonichia rmjUlus and other Infusorians, and finds that 

 in the i-egeneration which follows merotomy, multiplication of micro- 

 nuclei may occur, and that this iucrease may cause the regenerated in- 

 dividual to have more micronuclei than the number typical of the species 

 or race. In more than 50 p.c. of tlie experiments there was no nuclear 

 increase, so regeneration can go on without necessarily causing the micro- 

 nucleus to divide. 



The micronucleus may be regarded as an organella of some inde- 

 pendence during the asexual period, living in the plasma, as it were, 

 in a nutritive solution, and pricked on to division by some definite 

 change in its environment. This view is suggested by various facts : — 

 1. The cell can five very well without the micronucleus, in the case of 

 Paramecium., at least. 2. The division of the micronucleus can occur 

 independently of cell-division and macronucleus-division, e.g. in de- 

 pression (Popoff), in regeneration, and in conjugation. 3. The be- 

 haviour of the micronucleus in regeneration (in Stylonirhia) is not of 

 the nature of a regulation— in fact, its effect may be increase of the 

 micronucleus aljove the normal number. It may be that the micronucleus 

 is always ripe for division, if not throughout the whole of its resting 

 phase, at least long before the cell is ready for fission. There needs 

 only to arise the appropriate stimulus, i.e. the proper chemical or elec- 

 trical condition of the circumambient plasma, and mitosis will occur. 



Habits of Lacrymaria.f — S. 0. Mast has made a study of this in- 

 teresting spindle-shaped CiHate, w^hich has a phenomenal power of ex- 

 tending its " neck " and exploring in all directions with its " head " — 

 the knob-like protuberance bearing the mouth — the body remaining 

 meanwhile quiet and usually concealed in debris. The neck may 

 lengthen out to eight times the length of the body. 



Detached heads move like attached ones, except, of course, in draw- 

 ing back. Their movements are due to large oral cilia. The head 

 turns in all directions independently of stimulus. In swimming, the 

 body follows the head on its tortuous course. Stimulation of the an- 

 terior end causes contraction of the neck and backward movement ; 

 stimulation of the posterior end usually causes forward movement ; 

 practically all the other movements are random or trial movements, de- 

 termined largely by internal factors. 



The food seems to consist mainly of unicellular organisms, and there 

 is evident selection in feeding. The head does not swallow inorganic 

 substances, carmine or ink particles, and the like. With jerky, rapid, 

 random movements it tests every object within reach. During conjuga- 



* Proc. Eoy. Soc, Series B, Ixxxiv. (1911) pp. 332-44 (12 figs.). 

 t Journ. Animal Behaviour, i. (1911) pp. 229-48 (8 figs.). 



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