Phylum Pyrrhophyta [ 107 



are entozoic in frog tadpoles; some of them are non-pigmented. Three genera having 

 the typical single flagella are among the most familiar of flagellates. Euglena has 

 fusiform to cylindrical cells freely capable of writhing changes in shape. Phacus has 

 flattened cells with a rigid membrane. In Trachelomonas, the protoplast lies loose 

 in a rigid lorica which is often ornamented with spines; variations in the form and 

 ornamentation of the lorica have made it possible to distinguish a large number of 

 species. 



There are accounts of mitosis in Euglena by Keuten (1895), Baker (1926), Rat- 

 cliffe (1927) and Hall and Jahn (1929). All observers have seen within the nucleus 

 a large globule which divides as the nucleus does and appears to guide the separating 

 chromosomes. Keuten applied to it the term nucleolo-centrosome; the implications 

 of this term are not confidently to be accepted, and the body will better be called by 

 the neutral term endosome. RatclifTe's account of mitosis in Euglena Spirogyra is the 

 most detailed. It appears that division is initiated when the endosome buds oflE a 

 small granule which migrates to a position just within the nuclear membrane and 

 divides. The resulting granules may be regarded as centrosomes. The nucleus moves 

 forward within the cell and comes into contact with the cell membrane at the bottom 

 of the reservoir. Each centrosome appears to generate, just within the cell membrane, 

 a granule recognizable as a blepharoplast; the nucleus then withdraws from the cell 

 membrane, but the centrosomes remain connected to the blepharoplasts by rhizo- 

 plasts. The flagellum, already split at the base, divides throughout its length into two; 

 a new flagellum-base grows out from each blepharoplast and becomes fused to one 

 of the halves of the old one not far from the base of the latter. Meanwhile, withm 

 the intact nuclear membrane, the chromosomes and endosome are dividing. The 

 centrosomes are at the sides of the dividing nucleus. No spindle has been recognized. 

 Nuclear division is completed by constriction of the membrane. The cell divides by 

 constriction which proceeds longitudinally from the anterior end. The centrosomes 

 and rhizoplasts disappear, to be replaced during the next division by new ones. 



Hall and Hall and Schoenborn (in several papers, 1938, 1939) have reported 

 experiments on nutrition in Euglena. All species are capable of photosynthesis. Some 

 of them, surprisingly, have lost the capacity to synthesize amino acids which usually 

 accompanies photosynthesis; and there are transitional species in which some in- 

 dividuals possess the capacity to make amino acids and others do not, evidently as 

 heritable characters. 



Family 3. Astasiaea Ehrenberg Infusionsthierchen 100 (1838). Family Astasiidae 

 Kent Man. Inf. 1 : 375 ( 1880) . Family Astasiina Biitschli in Bronn. Kl. u. Ord. Thier- 

 reichs 1 : 826 ( 1884) . Family Astasiaceae Senn in Engler and Prantl Nat. Pflanzenfam. 

 I Teil, Abt. la: 177 (1900). Colorless organisms. Deflandre found the flagella sticho- 

 neme, as to the single flagella of Astasia and Menoidium, and as to one of the two 

 flagella of Distigma. Hall and Jahn (1929) found the flagella not swollen near the 

 base. The internal rod-shaped structures which characterize the following family are 

 absent. 



Belar (1915) described mitosis in Astasia, and Hall (1923) described it in 

 Menoidium. There is a blepharoplast at the base of the flagellum, and some prepara- 

 tions show a rhizoplast connecting this to a centrosome immediately outside the 

 nuclear membrane. The blepharoplast divides during the early stages of mitosis, and 

 the flagellum appears to divide lengthwise. The daughter centrosomes mark the loci 

 toward which the dividing chromosomes move. The chromosome number appears to 

 be 12. A dividing endosome like that of Euglena is present. 



