MICROSYMBIOSIS 77 



The responses shown by the algal symbionts are equally 

 interesting and significant. The free-living algae possess 

 a nucleus, besides pyrenoid and chloroplast. After the 

 algae have become s^Tubionts they gradually lose their 

 nuclei. "A parallel suggests itself between the green cells 

 of C. roscoffensis and the red blood corpuscles of the higher 

 vertebrates. As the red discs are enucleate, partial cells 

 budded off from the nucleate red cells, so may the green 

 cells be regarded as enucleate, partial cells budded off from 

 the outermost, nucleated green cells; and as the red blood 

 corpuscles are of limited life and speciahzed (respiratory) 

 function, so are the green cells of C. roscoffensis of limited 

 life and specialized photosynthetic function." This state- 

 ment, perhaps, does not convey the full significance of the 

 status of the algal symbionts. The morphological and 

 physiological responses indicated in algal symbionts will 

 be discussed in more detail in another chapter. 



Algal symbionts in the anneUd worms, apparently, have 

 never been observed. Bacterial symbionts, however, have 

 been described by a number of authors. These symbionts 

 have been called "bacteroids," and they have been credited 

 with connective tissue fibrillae formation. Cerfontaine 

 ('90) discovered these bacteria in the coelom of the dew 

 worm, and beUeved that they are the cause of the rapid 

 putrefaction that takes place in these animals after death. 

 Cuenot ('92) and K. C. Schneider ('02) investigated these 

 organisms and confirmed Cerfontaine's diagnosis of their 

 bacterial nature. Trojan ('19) investigated the bacteria 

 and observed their relationship to fibrillae formation, but 

 believed that they were "chromidia" derived from the 

 nucleus. Schneider, also, observed these bacteria in Nereis, 

 Sigalion and in marine polychaetes. Buchner emphasizes 

 the difficulty of distinguishing between bacteria, mitochon- 

 dria and mitochondria-Uke cell-inclusions. 



In the Bryozoa, yellow algae have been described in 



