POLYTOMELLA CITRI, SP. NOV. 227 



five definitive ones arise in much the same way, by the pairing of 

 ten chromatin granules which form a ring around the endosome. 

 Doflein analogizes this fusion with the conjugation of homologous 

 pairs of chromosomes in metazoan and metaphytan cells. 



Thus we see that the greatest similarity in the activity of two 

 cell-organs is not to be found in two organisms whose general 

 structure is most nearly alike, but in two that have the nearest 

 approach to identity in that particular organ. 



Encystment. There is a remarkable correspondence of the 

 encysted forms of the various species of this family. Pyrami- 

 monas delicatnlus and Spermatozopsis exsultans are the only ones 

 in which cysts have not been described. There is only one case 

 where division takes place within the cyst (Doflein, 1916). 

 Aragao did not find division in this same species. This author 

 met with the same difficulty that was encountered in the present 

 work, namely, that the cyst could not be stained. This fact is 

 probably responsible for the fragmentary study of this important 

 phase of the life history of the Polyblepharididae, as no adequate 

 account has heretofore appeared. 



In Polyblepharides and Polytomella citri the living organisms 

 have been watched during excystment and in both cases amoeboid 

 movement was observed for some minutes before any use was 

 made of the developing flagella. Dunaliella and Polytomella citri, 

 and probably all of their near relatives, leave the cyst wall behind 

 without dissolving it. The latter dissolves on one side in order to 

 gain freedom, but the remainder of the shell stays in the culture 

 for some time. 



Since the pioneer work of Guillermond and Meyer metachro- 

 matic granules have been described from bacteria to metazoa. 

 The fact that these granules not only increase greatly during the 

 early days of encystment, but also are dissolved, not thrown off, 

 before excystment indicates that they have some important role 

 to play in the life of Polytomella citri. 



CENTRIOLE AND BASAL GRANULES. 



The observations made on this subject in the present work are 

 as follows: There are two basal granules from which arise four 

 flagella. These granules divide during the telophase of mitosis. 



