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Mr. W. Gardiner. On the Gland- Cells [Nov. 19, 



protoplasm, increase of rale of rotation and wave movements, canse 

 the cell sap to be so disturbed, and as it were churned up, that drops 

 of the sap become cut off from the main mass, and at last the whole 

 of the sap is separated into numerous distinct portions which are 

 suspended in the protoplasm as oily drops, and are carried round in 

 the currents, presenting the appearance of moving droplets, pear- 

 shaped bodies, and long string-like processes. The cell in this con- 

 dition was known to Darwin as "aggregated." When movement 

 ceases, as often naturally occurs, owing to excessive secretion, or can 

 be induced by suddenly crushing the tentacle head, the variously 

 shaped masses become spherical, and lie quiescent in the protoplasm. 

 The aggregation produced by the action ,of ammonic carbonate is 

 somewhat different .from that brought about by feeding, and may be 

 spoken of as passive as opposed ,to active aggregation. In this case 

 the protoplasm abstracts water from the vacuole in the usual way, 

 and, steadily swelling, .chops up the tannin Joaded sap of the long and 

 narrow cells into separate globules. The rotatory movements cause 

 these globules to alter their form, bat the movements in question are 

 nothing like so vigorous as in the . food-stimulated gland, and the 

 globules are rarely, if ever, carried bodily about. 



When the protoplasm swells .and the cell becomes aggregated, the 

 latter always loses its turgidity, and the state of aggregation is 

 accompanied by a loss of water. Injection of water into the tissue 

 will at once stop aggregation and restore the cell ,to its normal condi- 

 tion. Sometimes after active secretion (48 hours), the movements of 

 the protoplasm of the .topmost tentacle stalk,cells will stop, and much 

 oB the protoplasm of each cell now collects to ,the end of the cell 

 nearest the gland. Mounting in water will then restore the move- 

 ments. It was found experimentally that the collecting of the proto- 

 plasm to one end was occasioned by the upward passage of water to 

 the gland. If a passage of water be set up in an opposite direction, 

 then the protoplasm collects to the opposite end. 



When the more rapid movements of the protoplasm commence 

 owing to stimulation, the plastoid usually becomes bent, and then 

 either contracts and assumes a lenticular form, or becomes separated 

 into two or more pieces each of which becomes lenticular. Later on 

 further contraction ensues, and the plastoid is carried round the cell 

 in the protoplasmic stream. The, more the iCells lose their turgidity, 

 the more does the plastoid tend to assume a spherical form. Its 

 spindle-shaped elongated form may, however, be restored by again 

 bringing about turgidity, e.g., by injection of water into the tissue. 

 Thus the plastoid may be regarded as a turgometer, since it indicates 

 the state of turgidity of the cell. On account of certain experiments 

 and observations the author is led to believe that all differences of 

 turgidity in cells are brought about by the protoplasm swelling and 



