THE GREEN ALG^E 633 



forms constitute the Polyblepharidaceae, thus unquestionably 

 show a very marked mixture of Chlamydomonad and Flagellate 

 characteristics. They are therefore regarded as very important 

 links in the chain connecting the green Algae with the 

 Flagellata (Dill 21). It seems probable that Polyblepharis with 

 its relatively simple shape and more numerous cilia is a more 

 primitive form than Pyramimonas, while Dunaliclla appears to 

 be most specialised. 



The next step carries us back into the group of the Flagellata 

 (Klebs 38, Senn 63), and we have now to seek for a possible 

 connection among the organisms of this group with the Poly- 

 blepharidaceae. Senn subdivides the Flagellata 1 into seven 

 groups, three of which are colourless, while four, which may 

 be styled the algal Flagellates (Chrysomonadineae, Crypto- 

 monadineae, Chloromonadineae, Euglenineae), are possessed of 

 pigments, whereby holophytic nutrition is possible. It is ob- 

 viously among these four groups that we must look for the 

 allies of the Polyblepharidaceae. Only two of them, the Crypto- 

 monadineae and Euglenineae, have a green pigment of the nature 

 of chlorophyll. Of these the Euglenineae may be dismissed at 

 once, since their organisation is too complex to admit of a close 

 comparison with the green Algae, and since starch, one of the 

 great characteristics of the algal forms hitherto considered, is 

 not the product of assimilation. We are thus left with the 

 Cryptomonadineae (Senn 63), which, as far as our present know- 

 ledge goes, include rather a diverse collection of forms. Of 

 these the genera Cryptomonas and Cliilomonas are of the most 

 interest from our point of view. Cryptomonas (fig. 1, n) occurs 

 both in fresh and salt water, is actively motile by means of two 

 cilia arising in a depression a little way behind the obliquely 

 truncated front end of the somewhat flattened ovoid cell, and is 

 provided with two parietal chloroplasts, which have the shape of 

 a shallow watch-glass and may be green or yellow or otherwise 

 coloured. Numerous hexagonal starch-grains (g) are apposed 

 to the inner surfaces of the chloroplasts. A nucleus is situated 

 posteriorly, and there are two contractile vacuoles at the front 



1 The most essential characters of the Flagellata lie in their motile condition 

 (with an often pronounced sedentary tendency), in the absence of a definite cell- 

 wall and the consequent more or less pronounced power of change of shape, 

 in the longitudinal division, the scarcity of sexual reproduction, and the faculty 

 of encystment (cf. Klebs 38). 



