288 C. CLIFFORD DOBELL. 
nuclei of Arcella, Polystomella and Entamceba must 
likewise be parasites.” Nor even from his description can I 
regard the “ fertilisation” of Amceba proteus as “ strik- 
ingly similar to that of Hntamceba coli.” The sexual 
phase—if it exist—in Amoeba proteus remains still un- 
known. 
The facts about “ chromidia” in Amoeba are therefore 
much too doubtful to allow of any profitable discussion at 
present.! 
(4) Rhizomastigina.—In the mastigamoebe (Masti- 
THxT-PIG. 4. 
Mastigella vitrea Goldschmidt, (a mastigamceba). N. nucleus; 
Ch, chromidia ; nu, nucleolar substance; g, fully-formed 
gamete. (Modified from Goldschmidt, ’07.) 
gella and Mastigina) we have one of the most carefully 
described cases of chromidia formation (Goldschmidt, ’07). 
Chromidia—consisting of both “nucleolar substance” and 
chromatin—are extruded from the nucleus. In the cytoplasm 
they become aggregated at certain points and form gamete 
nuclei (text-fig. 4). ‘The main nucleus remains behind, for a 
greater or less period, but in the end perishes. 
(5) Radiolaria.—A structure lke the chromidial net of 
Thalamophora was long ago described in Acanthometrids by 
' Chromidia are described in A. diploidea (Hartmann and Niigler, 
08) and some other species, but their significance seems to me to be 
very questionable. 
