634 SCIENCE PROGRESS 



end of the cell. Cryptomonas is capable both of holozoic and 

 holophytic nutrition. Reproduction takes place by longitudinal 

 division — in most cases apparently while the organism is in a 

 kind of Palmella-stagQ and enveloped by stratified mucilage, 

 which sometimes shows the reactions of cellulose. Oval or 

 rounded resting-cysts, having a coarse cellulose-membrane, are 

 formed in response to unfavourable conditions. The genus 

 Chilomonas (fig. i, o) differs principally in being colourless; the 

 chloroplasts are replaced by leucoplasts, numerous starch-grains 

 generally occurring in the protoplasm. The method of nutrition 

 is saprophytic. Both genera agree with other Flagellates in 

 lacking a cell-wall, but they do not possess as marked a power 

 of changing their shape as do other members of the group. 

 The prevalence of the motile phase in the life-history is also a 

 rather striking feature. 



In their possession of chlorophyll and in forming starch the 

 Cryptomonadineae show significant analogies to the green Algae, 

 and there are certain other points of resemblance to which 

 attention may be drawn (cf. also Scherffel 58). The group in- 

 cludes both holophytic forms and saprophytic forms producing 

 starch (cf. Polytomaceae, p. 631). The two parietal chloroplasts 

 of Cryptomonas are readily derivable from a basin-shaped chloro- 

 plast, like that of the Chlamydomonads, by imagining splitting 

 to have taken place, so that both Cryptomonadineae and 

 Chlamydomonadineae {i.e. in the wide sense, including Poly- 

 blepharidaceae, etc.) may be derived from a common type with 

 a basin-shaped chloroplast. In view of the fact that the Chlamy- 

 domonadineae, although otherwise obviously of a predominant 

 algal character, have the motile phase as the dominating one 

 in the life-history, we may expect the same to be the case in 

 the Flagellate ancestors, so that it is quite in accord with the 

 theory we are endeavouring to support that the Cryptomonads 

 show little of that sedentary tendency which is sharply marked 

 in certain other Flagellate groups {e.g. Chrysomonadineae or 

 Chloromonadineae, Senn 63). Other minor features that lend 

 support to a relationship between Cryptomonadineae and 

 Chlamydomonadineae are the limited power of change of shape 

 in the former group (cf. Polyblepharidaceae), the two contractile 

 vacuoles at the front end of the cell, the two cilia of equal 

 length (characteristic of the Isokontae among the green Algae, 

 (cf. the second part of this article), and the occurrence of 



