ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 261 



author affirms, or has direct evidence to affirm, either that zoogonidia 

 are produced in the cells, or that the free germinating bodies are 

 escaped zoogonidia ; but these circumstances are mentioned as showing 

 how necessary it is that VaucJieria should again become the subject of 

 investigation for the purpose of discovering beyond doubt what is the 

 cause and true interpretation of this unsuspected septation of the 

 filaments. 



Rejuvenescence of the Thallus of Vaucheria.* — It has been 

 known since the time of Hanstein that the thallus of VaucJieria 

 remains unseptated so long as it is in a purely vegetative condition ; 

 but that if a filament is injured, the protoplasm of the uninjured part 

 immediately contracts, and protects itself by a septum which shuts it 

 off from the injured part. J. Schaarschmidt has repeated Hanstein's 

 observations with similar results. Filaments of V. sessilis, when in- 

 jured, immediately repair themselves in this way, but no longer have 

 the power of reproduction ; they break up into gemmae, which remain 

 for a shorter or longer time in this condition, and then germinate, 

 producing new filaments. Gemmge are also formed on uninjured fila- 

 ments, going through a great change of form before germination. In 

 this condition they greatly resemble Gongrosira, but still more the 

 protoplasm-tubes which are put out from the zoosporangia on the 

 rhizoids of Botrydium granulatum. 



A similar but less marked power of rejuvenescence was observed 

 by Schaarschmidt in Conferva homhycina. A portion of the contents 

 of the injured apical cell invested itself with a double membrane, and 

 separated itself from the injured cell. 



Assimilation of Hsematococcus.t — T. W. Engelmann has applied 

 his bacterium-method for the determination of the elimination of free 

 oxygen J to decide the question whether algae in the red resting con- 

 dition, especially Mcematococcus and Chroolepus, disengage oxygen or 

 not ; Kostafinski having stated § that the former of these organisms 

 has the power of assimilating, although destitute of chlorophyll. By 

 the method named, Engelmann determined the elimination of oxygen, 

 but also that chlorophyll is contained in a peripheral layer of the 

 protoplasm of Hcematococcus, the quantity being, however, always 

 small. The green colour is usually masked by the red pigment, 

 although occasionally evident. 



In the Oscillarieae and diatoms, on the contrary, the presence of 

 chlorophyll could not be determined in this way ; and the chlorophyll, 

 if present, is mixed with other colouring matters which have also 

 assimilating properties, or chemical compounds are present which are 

 affected by light in the same way as chlorophyll, but differ from that 

 substance in respect to the relative activity of the different rays of 

 light. For these hypothetical substances he proposes the name 

 " chromophylls." 



* Magyar novenytani Lapok, vi. (1882) pp. 10-13. See Biol, Centralbl., ii. 

 (1882) p. 513. 



t Bot. Ztg., xl. (1882) pp. 663-9. 



J See this Journal, i. (1881) p. 962, ii. (1882) p. 661. 



§ Ibid., i. (1881) p. 930. 



