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f 



12 



MISS B. M. BRISTOL ON 



tlie posterior part of tlie zoogonidiiim. Within a fow hours the cells 

 completely round tlieuiselvos off, lose their cilia, and acquire a ihin cell-wall ; 

 subseijuentlj tliej develop by gradual stages into ordinary vegetative cells* 



IV. Chlorochythium Facciola/E (13orzi)j Bristol. 



Since the first description o£ this alga under the generic juune Ceidrosplurra 

 by Borzi* in 1889, it lias boon recorded by IJansgirgf from Bohemia and by 

 West X fi'oiu the soutli of England , but nothing has been added to Bor/A's 

 original description. The alga occurs aggregated in a more or less diffuse 

 stratum among tlie colonies of various members of the Oscil]atoriacea\ The 

 chloroplast is evidently like tliat described in this paper for C. pamdoxum^ 

 since Borzi states that the chlorophyll is differentiated into numerous 

 cylindrical rods, some straight and some wuv}^, winding inwards towards the 

 centre of the cell, where there is a circular colourless area, and accommodating 

 themselves against the inner surfacf^ of the cell-wall by their circular base. 



Eventually the vegetative cell increases in size, and develops into a 

 zoogonidano-iuni with a much thickened striated wall. This boars 1-3 small 



G^" ^ 



conical cellulose projections on its inner surface and a single callous projection 

 on its outer surface. Zoogonidia arise which are set free separately through 

 a small pore fornu^d by the dissolution of some part oE the zoogonidangium- 

 wall. The whole of the cell-contents are used in the formation of the 

 zoogonidia, witli the exception of the hitMnatochrome, winch remains in 

 the cell-cavity as a few guttides of red oiL The zoogonidia develop directly, 

 without fusion, into thin-walled vegetative cells, the confents of which on 

 attaining a certain size divide simiTltuneously to form a number of aplauo- 

 sporesj w^hich are set free by the gradual dissolution of the whole cell-wall. 

 Several generations of aplanospores are produced before the vegetative cells 

 finally develop into zoogonidangia again. 



Hansgirg set up a variety {ir re gal avis) of this species to include those 

 individuals which he found witli the ordinary form, which were rather larger, 

 had a somewhat thicker wall than usual, and were irregular in shape. In 

 view of the instability in the shape of the cells which has recently been 

 shown to exist among these alga^, such a variation cannot logically be 

 considered to justify the setl hig up of a special variety • 



C. Facciola.e var, min'OK, nob. {CentrosphccrcG var., Borzi) was considered 

 byBorz]§ to be an independent species of the genus Centrospliccra. The 

 alga thus described agrees with C. FaccioJme in every particular of its 

 structure and life-history, differing only in the size of its cells. It was 

 found in stagnant deep sea-water associated with other algpe^ and can 

 certainly be considered at most only a variety of C. Facciolacc. 



♦ Borzb Studi Algologici, Fasc. i. pp. 88-97. 

 t Hanpgirgj Prodr. p. 124. 



X West, G. S. 'British Freshwater Algfp/ Cflmb. Biol. Series, p. 199 (1904), 

 § Borzi, he, cit. 



