OTHER PROTOPLASMIC MOVEMENTS 301 



difference arises in the external medium, whereas a drop of a mixture of 

 oil and potassium carbonate shows movement when surrounded on all sides 

 by a homogeneous medium, water. Even if the locomotory energy is 

 actually supplied by the cytoplasm the nucleus might easily exercise 

 a directive influence upon it, and so determine the direction of movement. 



It is, therefore, not surprising that doubt should exist as to whether 

 the slow translocatory movements of nuclei and chloroplastids are always 

 passive in character or not. The nucleus may be passively carried to any 

 point where an accumulation of protoplasm is produced either by traumatic, 

 chemical, or other agencies. Even without such accumulation a passive 

 movement of the nucleus is as readily possible as an active one. Some 

 authors assume the former to be the case, others the latter l , but no critical 

 experiments have as yet been performed. The occasional amoeboid or 

 gradual changes of shape of the nucleus appear, however, to be active in 

 character, but even here interaction with the surrounding cytoplasm may 

 aid in their production 2 . The same applies to the chloroplastids, whose 

 movements in response to illumination may either be active or produced 

 by a directive utilization of the motile energy of the cytoplasm. In the 

 same way it is impossible to say whether the movements of the chromo- 

 somes are active or passive, or are compounded of both. 



The special elongated, lobed, twisted, or even spirally coiled shapes 

 sometimes assumed by nuclei can often be seen to be independent of the 

 shape of the cell, and not to be mechanically impressed upon the nucleus. 

 The nuclei of animals more often show amoeboid movements than those of 

 plants 3 , but whether amoeboid activity plays a part in the passage of the 

 reproductive nuclei from the pollen-tube to the ovum and embryo-sac is 

 still uncertain 4 . The same applies when the nucleus passes from one cell 

 to a neighbouring one during cases of vegetative fusion 5 . It is quite 

 possible that the fibrillae appearing during cell-division, but which may 

 also be produced in various ways, may be capable of producing internal 

 movement by their supposed contractile activity. These structures are, 

 however, transitory in character, and their tendency to shorten is of similar 



1 Cf. Hanstein, Mittheil. ii. d. Bewegungserscheinungen des Zellkerns, 1870, p. 224 (reprint 

 from Sitzungsb. d. Niederrh. Ges.) ; Berthold, Protoplasmamechanik, 1886, pp. 150, 164; Haber- 

 landt, Function u. Lage d. Zellkerns, 1887, p. 103 ; Behrens, Bot. Ztg., 1890, p. 100. 



2 Cf. Molisch, Studien ii. d. Milchsaft u. Schleimsaft, 1901, pp. 87, 107; Bot. Ztg., 1899, p. 177; 

 Haberlandt, 1. c., p. 124; v. Wasielewski, Jahrb. f. wiss. Bot., 1902, Bd. XXXVIH, p. 415; Ewart, 

 Journ. Linn. Soc., Vol. xxxi, 1896, p. 448. 



3 [The nuclei of such parasitic plants as Cuscuta, Lathraea, and Orobanche seem to show 

 amoeboid movement more commonly and markedly than those of ordinary plants, but whether this 

 is connected with the rich nitrogenous nutrition or the general activity of metabolism is uncertain.] 



4 Cf. Mottier, Fecundation in Plants, 1904, p. 176. 



5 Cf. Strasburger, Jahrb. f. wiss. Bot, 1901, Bd. xxxvi, p. 551; Koernicke, Sitzungsb. d. 

 Niederrh. Ges., March, 1901. 



