242 University of California Publications in Zoology [Vol. 19 



among flagellates, of mitosis. There is not sufficient evidence yet to 

 generalize, but there is a probability, previously expressed by many, 

 that with a fuller knowledge of flagellates, amitosis as a normal 

 method of cell division in Protozoa will be reduced to a minimum. 

 All work on flagellates and rhizopods in which amitosis has been 

 recorded, should be reworked carefully and patiently, for the meta- 

 phase spindle is not a structure of long duration, very few instances 

 being met with in the vast number of vegetative and karyokinetic 

 individuals, and the various stages and figures of the prophase are 

 readily capable of erroneous interpretation. 



There are several important problems related to the differential 

 division of the karyosome. In the first place it in no way involves the 

 question of amitosis as a type of reproduction. 



That there is here any phenomenon of chromatin reduction, homolo- 

 gous to maturation, must be regarded with equal skepticism. The 

 phenomena of sex have been established for the Phytomonadina for 

 years (Dobell, 1908). The nuclear details of the sexual process in this 

 group are still hard to explain. In other flagellates sex phenomena 

 have received little confirmation. Maturation, such as is regarded as 

 necessary in sexual reproduction among higher plants and animals, 

 has had little corroborative evidence among flagellates. Dobell (1908) 

 worked out the life cycle of Copromonas subtilis and figures nuclear 

 extrusion of chromatin in the form of two polar bodies. These are 

 not described as the products of mitosis, however. On critical exami- 

 nation Dobell 's work is not convincing. His evidence is inadequate 

 and thus far has not been verified. Goldschmidt (1907) described 

 similar phenomena for Mastigella vitrea. His observations are less 

 satisfactory than Dobell 's. Schaudinn (1904) in error extended the 

 sexual process to Trypanosoma noctuae. 



Nuclear extrusion of chromatin is, however, a common phemonenon 

 in flagellates and protozoa generally. Work on Trichomonas (Kofoid 

 and Swezy, 1915) reveals chromatin extrusion in each of these forms. 

 Among Amoeba of the Umax group (Alexeieff, 1911&, 1912a, 1912b), 

 a similar extrusion occurs. But all of these extrusions as described. 

 with the exception of Copromonas, seem to have no relation to matura- 

 tion phenomena. 



Collodictyon (pi. 10, figs. 29-36) presents a clear case of separation 

 of chromatin from that which organizes for mitosis in the differential 

 division of the karyosome (pi. 10, fig. 32). In one instance the 

 macrokaryosome is seen in a state of division (pi. 10, fig. 33) very 





