638 SCIENCE PROGRESS 



shaped chloroplast and a large eye-spot, which is present both in 

 the resting and motile cells. The latter have four cilia (cf. Pyra- 

 mimonas), and after a period of movement become attached by 

 their ciliate end, which gradually produces a long stalk at the 

 lower extremity of the cell. By oblique longitudinal division 

 of the cells the branched colony is gradually produced. To this 

 family we may perhaps also refer the genus Chlorangium* 

 which Oltmanns places among the Chlamydomonadaceae and is 

 of interest because the cells have two lateral chloroplasts (Stein 

 64). Both genera are readily derivable from the Chlamydomonas- 

 type, and are chiefly interesting because they are the algal 

 analogues of various Flagellate forms (such as Dinobryon, 

 Colacium, etc.), although themselves not much beyond the 

 Flagellate boundary. 



The next series, that of the Tetrasporaceae (so called because 

 of the prevalent arrangement of the cells in fours), is more 

 important. The typical representatives of this family (i.e. Tctra- 

 spora and Apiocystis) are easy to derive from Chlamydomonas 

 by assuming a prolongation of the palmelloid phase, such as 

 is well shown by C. Kleinii (Schmidle 59); indeed, in C. apio- 

 cystiformis (Artari 2, p. 39) we even have a Palmella-stage very 

 closely resembling the Tetrasporaceous genus Apiocystis. Both 

 in this genus and Tetraspora (Chodat 13) we have cells, showing 

 all the characteristic features of a Chlamydomonas except for 

 the eye-spot and the cilia, embedded in considerable numbers 

 in an attached mass of mucilage, which in Tetraspora (fig. 2, d) 

 is more or less irregular in shape, while in Apiocystis (fig. 2, e) 

 it has a characteristic pear-shape. When the cells are liberated 

 as motile elements in asexual reproduction it is very hard to 

 distinguish them from Chlamydomonas-ind'ividua\s. Apart from 

 this, one of the most interesting points about the Tetrasporaceae 

 are their pseudocilia, which in Tetraspora (Schroder 61) extend 

 only up to the surface of the mucilage enveloping the colony 

 (fig. 2, d), while in Apiocystis (Correns 15) they project some 

 way beyond it (fig. 2, e), the projecting portion being provided 

 with a special mucilage-sheath (not shown in the figure). These 



1 It seems a little questionable whether the affinity between Chlorangium, 

 Chlorodendi'on and Chlamydomonas is really close enough to warrant placing them 

 in the same order. The first of these genera seems more referable to the 

 Cryptomonad line with its two lateral chloroplasts than to the Chlamydomonad 

 line, to which Chlorodendron undoubtedly belongs. 



