lOOl SUMMARY OF CURRENT RESEARCHES RELATING TO 



sexual and a non-sexual mode of reproduction ; the latter by zoosiioros, 

 the former by zoogametes, which resemble the zoosj)orcs but are smaller. 

 The process is exceedingly similar to that in Chlamydomonas Beinhardti 

 Dang. 



Chlamydomonas.* — ^l. P. A. Dangeard gives a review of the species 

 belonging to tliis genus, which amount to four, two of them being new, 

 viz. C. Ecinhardti and C. Morieri. He divides the genus into two 

 sections, according as the membranes of the zoogametes serve to form 

 the membrane of the zygospore, or the oospore surrounds itself with a 

 membrane of its own, the former section, including C. Beinhardti and 

 muUifiUs, the latter C. pulvisculus and Morieri. 



In C. Beinhardti the biciliated zoogametes are indistinguishable 

 before conjugation ; tlie zygospore contains corpuscles which have often 

 been mistaken for nuclei. In C. multijilis Fres., the zoogametes have 

 four cilia ; the zygospore breaks up into a colony resembling that of 

 Pleurococcus. In C. puhisculus Miill., the female zoogametes are dis- 

 tinctly larger than the male. C. Morieri displays a peculiar kind of 

 conjugation. When the zoogametes come together, a perforation takes 

 place in their cell-walls ; their cilia disappear ; and the protoplasts of 

 the two cells fuse together through the perforation. This species also 

 developes non-sexual zoospores, which become resting-spores in the 

 winter. 



Considerable doubt rests upon other species which have been included 

 in the genus. 



Chlamydococcus pluvialis.t — M. P. A. Dangeard reviews the pre- 

 vious observations on this organism (^Protococcus pluvialis A. Br., 

 Hsematococcus lacustris Gir.). He confirms the observations of Eosta- 

 finski as to the formation of two kinds of zoospore, microzoospore and 

 macrozoospore, and compares tlie structure to that of Goniinn pectorale ; 

 the only difierence being that while in that genus the macrospores and 

 microsjiores remain united in one plane, in Chlamydomonas and Chlamy- 

 dococcus they separate from one another. The zoospores of C. pluvialis 

 become encysted in the winter, aud then constitute resting-spores of a 

 red colour, in which condition they may remain dormant for a very long 

 period. Before germinating tlie external red layer again becomes green, 

 and divides into zoospores which escajje by the rupture of the membrane 

 of the resting- spore. The statement of some observers that conjugation 

 takes place between the macrozoospores the author believes to rest on 

 an error of observation ; as is also the case with the so-called amoeboid 

 phase. 



Cell-membrane and Gelatinous Envelope of Desmidie8e4 — Herr P. 

 Hauptflcisch has made a series of very careful observations on the 

 investing cell-wall and gelatinous sheath of the desmids. The two 

 halves of the cell are not exactly symmetrical, the plane of symmetry of 

 one half lying at an acute angle to that of the other half. Hence the 

 two cells which remain connected after division, or the filament where 

 a number are united together, always exhibits an evident torsion. 



The wall of a desmid-cell always consists of two separate pieces, 



* Bull. Soc. Linn. Nnrmandie, i. 188G-7 (1888) pp. 151-8. t Ibid., pp. 43-9. 



X ' Zellmembran u. Hiillgallerte d. Desmidiaceen/ 78 jip. and 3 pis., Greifswald, 

 1888. See Hedwigia, xxvii. (1888) p. 199. 



