318 SUMMARY OF CUlUtENT RESEARCHES RELATING TO 



attached to the costae. Perhaps there is a strip of dotted membrane 

 attached to or forming a part of the girdle, and other dotted mem- 

 branes attached to the costas, l)ut he has no direct evidence of this. 

 He holds that the dots are concavities, as one might expect by analogy, 

 because fracture takes place across them, and when seen sideways on 

 the rounded edge of a curved membrane the curve of the concave out- 

 line is obvious. Five photographic figures illustrate the author's con- 

 tentions. 



Chlorochytrium grande.* — B. Muriel Bristol gives an account of 

 the life-history and cytology of Chloi'ochytrium grande, a new proto- 

 coccaceous alga, collected in a dyke in West Yorkshire. She gives the 

 following summary of her results : — 1. In rain-water rapid multiplica- 

 tion of the plant takes place by means of aplanospores, and the cells are 

 thin-w^alled. In mineral salt-solutions aplanospores are formed more 

 rarely, and the cells become converted into large zoogonidangia with 

 very much thickened walls. In distilled water an enormous thickening 

 of the walls takes place. 2. The vegetative cells are spherical, sub- 

 spherical, or ellipsoid, 65-75 fx. in diam., with a wall of fairly uniform 

 thickness consisting of an inner cellulose and an outer pectic layer. 

 They contain a wide-meshed cytoplasmic reticulum, with a large central 

 nucleus and a single massive chloroplast, which is raised into numerous 

 rounded lobes at its surface and occupies practically the whole cell 

 except the nucleus. The cells contain oil, numerous granules of starch, 

 and a variable number of pyrenoids. 3. Propagation takes place by 

 simultaneous division of the contents of a cell into aplanospores, pre- 

 ceded by numerous successive mitotic divisions of the nucleus of the 

 cell. The chromatin of the resting-nucleus is in the form of a karyo- 

 some. 4. The zoogonidangia are very large, averaging 130 //. in diam. 

 The wall bears one to two rounded external pectic projections, and one 

 to several internal cellulose projections which are frequently large and 

 may be branched within the cytoplasm, which is correspondingly dis- 

 torted. Starch, oil, and pyrenoids are all present. 5. Zoogonidia- 

 formation takes place by the successive bipartition of the contents of 

 the mother-cell into numerous biciliate oval or pear-shaped bodies, 

 which escape through a vesicle in the zoogonidangium wall. They 

 develop directly into vegetative cells. 6. The alga is established as an 

 independent species on account of the very large size of the zoogonid- 

 angium and the great thickness and irregularity of its wall. 7. The 

 generic names Endospliaera Klel)s (1881), Scotinosphxra Klebs (1881), 

 Centrosphsera Borzi (1883), are unnecessary, since the algas thus named 

 can quite satisfactorily be included within the single genus Chlorochy- 

 trium Cohn (1874) ; and the generic distinctions put forward by Klebs 

 and Borzi are inadequate for their retention as independent genera. 

 The new species described has therefore been named Ghlorochytrium 

 grcvnde, rather i\i2a\ Centrosphsera grandls. 8. Phyllobium sphagnicohi is, 

 a ccenocyte, containing a reticulate mass of cytoplasm in which are 

 embedded numerous small granules of chromatin, and in the meshes of 



* Ann.Bot., xxxi. (1917) pp. 107-26 (2 pig. and figs.). 



