ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 439 



the later stages, nor does it prevent a certain amount of mixture of the 

 cytoplasm of the conjugating individuals. 



In contrast to ciliate Infusorians, the difference between the migra- 

 tory or male germ-nucleus and the stationary or female germ-nucleus is 

 in Dendrocnmetes reduced to a minimum. It is possible that in all cases 

 one germ-nucleus traverses the membrane and the other does not, so 

 that the distinction remains, but the two nuclei are as nearly neuters as 

 can be. Moreover, the fusion of the germ-nuclei takes place during a 

 resting and not in a mitotic state. The ordinary vital processes are not 

 affected by the conjugating act. 



Plate's observation of the occasional occurrence of a conjugation of 

 three individuals is confirmed. The mixing of the cytoplasm in the 

 conjugative process is also confirmed. It seems probable that the sexual 

 stimulus affects the two individuals simultaneously and that there is no 

 differentiation of sex. 



Hickson gives a detailed account of the two or more, usually three, 

 micronuclei and their mitosis. 



Whatever difficulties there may be in finding an explanation of the 

 fact, there can be no doubt that the meganuclei do, during conjugation, 

 meet aud become continuous. The junction lasts a very short time and 

 it is probably followed immediately by disintegration. The new mega- 

 nucleus is formed from one of the four nuclei produced by the second 

 division of the germ-nucleus. In this formation there are remarkable 

 processes of elimination and recovery of chromatin. 



The paper concludes with an interesting chapter of general con- 

 siderations, leading on to the conclusion that the body of Dendrocometes 

 is no more a single independent cell than is the embryo-sac of an 

 angiosperm. 



Osmotic Phenomena in Infusorians.* — P. Enriques has experi- 

 mented with Opalina ranarum, Vorticella nebulifera, Halteria, Ghilodon, 

 and Gastrostyla steinii, and finds that when these Infusorians are trans- 

 ferred from one medium to another of different tonicity, they exhibit at 

 first a change of volume due to the passage of water through their cell- 

 wall, osmotically impermeable to salts ; and then a change in the opposite 

 direction due to the non-osmotic reception of water and salts (absorbed 

 or excreted) which may temporarily more than counteract the initial 

 changes. Infusorians without mouth and gullet, e.g. Opalina, are 

 impermeable by endosmosis to sodium chloride dissolved in the water. 



Foraminifera.f — F. Chapman has made students of zoology his grate- 

 ful debtors by this excellent account of the Foraminifera — well illustrated 

 and printed, and reasonably cheap. After some introductory chapters 

 on the position, structure, reproduction, and classification of Forami- 

 nifera, the author gives a systematic survey of the ten well-established 

 families. Then follow chapters on geological range and geographical 

 distribution, on collecting and mounting. The book ends with a biblio- 

 graphy. We have had the pleasure of using the book in the laboratory, 

 and can testify to its convenient utility and clearness. 



* Atti (Rend.) R. Accad. Lincei, xi. (1902) pp. 340-7. 



+ The Foraminifera: An Introduction to the Study of the Protozoa, London, 

 3902, 8vo, xv. and 354 pp., 14 pis. and frontispiece, and 42 figs. 



