CHROMIDIA AND THE BINUCLEARITY HYPOTHESES. 283 
Actinospherium (text-fig. 1). They are in the form of 
chromatin strands or granules lying in the cytoplasm, and 
are formed from the nuclei. Their formation may be induced 
either by over-feeding or by starving the animal. ‘They are 
simply metabolic products—explicable, perhaps, by Hertwig’s 
“ Kernplasmarelationtheorie” (cf. Hertwig, ’03,  ete.). 
Hertwig named them “chromidia” in 1902. He further 
found that, during degeneration, the nuclei of Actino- 
sphezrium became enormously enlarged and hyperchromatic, 
and finally underwent fragmentation into chromidia (Hertwig, 
00, 704; Howard, 08). These are the essentials.! 
(2) Let us pass on to the Thalamophora. Hertwig (’87) 
Trxtr-rre. 1. 
A portion of an Actinospherium in a chromidial condition. 
N. nucleus: Ch. chromidia, formed from the nuclear chro- 
matin. (The entire cytoplasm is filled with chromatin frag- 
ae lying in the walls of the alveoli.) (After R. Hertwig, 
noted in Arcella an arrangement of extra-nuclear chromatin 
similar to that which he had already recorded in Radiolaria 
(videinfra). He described a “nuclear band” in addition 
to the vegetative nuclei. 
Chromidia were discovered in Polystomella by Lister 
(94, 795), but he was unable to decide upon their significance. 
Rhumbler (94) probably observed chromidia in Saccam- 
mina, but was likewise unable to interpret their meaning. 
The chromidia in Polystomella were also seen by Schaudinn 
(95a). 
In 1899 Hertwig succeeded in fully tracing the develop- 
1 Similar processes occur in Actinophrys also (Distaso, ‘08), 
