ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 259 



Nuclei of Uroleptus mobilis. — Gary N. Calkins {Journ. Exper. 

 Zool., 1919, 27, 298-3r)7, 95 tigs.)- This Hypotrichous Ciliate has 

 eight macronuclei. In preparation for division of the unit they fuse into 

 one. Prior to the division of the unit this divides twice ; after division 

 of the unit each of the four divides again so that eight result. The 

 divisions are amitotic. The micronuclei vary in number from two to 

 six ; they do not fuse in preparation for cell-division, but the number is 

 reduced to two, probably by absorption. With cell-division the two 

 nuclei divide. One of the four may degenerate, or all may divide. In 

 the latter case two degenerate while six divide to form twelve, six for each 

 daughter-cell. Of these six, one or two may degenerate. Divisions are 

 always mitotic, with eight single or partially fused chromosomes. Whether 

 the chromosome division is transverse or longitudinal could not be 

 determined. 



Psedogamous conjugation lasts from twenty-eight to thirty-six hours ; 

 the macronuclei are retained, but degenerate and are absorbed. Four 

 micronuclei is the usual number in conjugants. All or some form first 

 maturation spindles. The prophase stage for these is a characteristic 

 nucleus, termed the parachute nucleus, with an intranuclear division 

 centre. The second maturation-spindles are usually two in number, 

 each with eight chromosomes arranged in four pairs. Division separates 

 the members of each pair, resulting in reduction in the chromosomes 

 from eight to four. All the four may undergo the third division, or 

 one or two may degenerate. Fusion of pronuclei begins while in the 

 vesicular state ; before fusion is complete the pronuclei assume a spindle 

 form, which becomes the first division-spindle, with eight chromosomes. 

 The first two nuclei divide again ; one gives rise to the functional 

 micronuclei, the other to one micronucleus which degenerates and to one 

 which form the new macronucleus. The conjugants separate at this 

 stage, J. A. T. 



"O^ 



Influence of Blood-serum on Colpidium colpoda. — Sophie Pecker 

 {Pfluger's Arch. Ges. Physiol, 1916, 163, 101-46, 1 pi., 39 figs.). The 

 most striking effect is a deformation of the cysts of this Ciliate Infu- 

 sorian when they are brought into contact with blood-serum. They 

 take the form of capsules enclosing one spore or several spores. There 

 seems to be a plasmolytic action on the part of the serum. J, A. T. 



Races of Colpidium colpoda. — S. V. Prowazek {Arch. f. Protisten- 

 kunde, 1916, 36, 72-80, 14 figs.). There seems to be a great delicacy 

 after conjugation. There is much individual inequality in resisting-, 

 power to poisons. Modification-differences may be induced, but they 

 do not persist for more than a limited time. Some of the differences 

 previously regarded as mutations behave more like modifications. . 



J. A. T. 



Amoeboid Variations in Flagellates. — A. Pascher {Archiv. 

 Protistenkunde, 1916, 26, 8-116, 3 pis., 14 figs.). Some Flagellates 

 readily become stationary and holophytic, but some may become amaboid. 

 This is very marked in some which lose their flagella and zoospores. 

 The author describes Heterolagynion Pascher, which recalls a Rhizopod, 



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