THE PROTEOMYXA 



This does not imply, however, that the organism is at this stage 

 devoid of nucleoplasm, but that the nucleoplasm is not concentrated 

 in the form of a definite nucleus or kernel but is scattered or 

 diffused. This conception may be expressed by saying that the 

 stage is akaryote but is not moneran. There is no nucleus but 

 there is nucleoplasm. In Amoeba, Pelomyxa, and others in which 

 such a stage occurs the nucleus is present during the greater 

 part of the life-cycle, the akaryote stage being antecedent only to 

 nuclear multiplication or gametogenesis. 



In the Proteomyxa, on the other hand, the akaryote condition is, 

 as a rule, of much longer duration, and it is possible that in some 

 cases the diffused nucleoplasm or scattered chromidia do not collect 

 together in any stage to form a defined nucleus. 



It seems probable, then, that the protoplasm of the Proteomyxa 

 really represents the protoplasm of the higher Protozoa and 

 Metazoa plus the substance of the nuclei. It is a substance which 

 van Beneden (9) in 1871 proposed to call "the plasson," that is, 

 the formative substance "which is capable of becoming, either in 

 ontogenetic course or in phylogenetic course, monocellular elements 

 after that the chemical elements of the plasson have been separated 

 to constitute a nucleus and a protoplasmic body." 



Our knowledge of the nucleus or chromidia of the genera that 

 are here grouped together in the class Proteomyxa is at present 

 very scanty. Vampyrellidium is said to have a nucleus in all stages 

 of its life- history. Zopf states that a definite clear nucleus is 

 present in all species of Vampyrella, but it is often obscured by 

 chlorophyll and other bodies in the cytoplasm. There seems to be 

 little doubt, however, that the nucleus is not present in all stages 

 of the vegetative life of Vampyrella, as several observers who 

 have carefully re-examined its structure have failed to find any 

 definite nucleus. Recently, however, Dangeard (13) has shown 

 that nuclei are present in the cysts, and that they divide by karyo- 

 kinesis. In Tetramyxa there are said to be minute nuclei, but these 

 are probably chromidia. In Plasmodiophora true nuclei are un- 

 doubtedly present at the time of spore-formation, as they have been 

 observed to divide by karyokinesis. It is probable also that a 

 defined nucleus is present during the flagellate and amoebula phases 

 of most of the Proteomyxa (Fig. 8, B, H), but it is clear that for 

 a time during the plasmodium stage the nuclei are disintegrated. 

 In Endyonema nuclei appear to be wanting during the active vege- 

 tative phase in the filaments of its host -plant (Lingbya), but 

 definite nuclei are constituted when the body contracts in the 

 formation of the zoocyst. 



Many of the genera included in the group have been seen only 

 once, and we are still in ignorance of their nuclear condition, but 

 in Gymnophrys, Biomyxa, Gloidium, Leptophrys, and Protamoeba, 



