78 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



Zoobothrium pellucidum by Brandt ('83). Brandt, also, 

 described yellow-brown amoeboid algae in the echinoderms 

 (Echinocardium) . Geddes (79) described brown amoeboid 

 bodies in various echinoderms. Holothurian larvae also 

 are supposed to contain yellow algae, present as clumps. 

 Brandt observed that when the larva dies the color disap- 

 pears at once. The bodies can be demonstrated after 

 death however by means of iodine. Semon raised the 

 question whether they are algae or pigment cells. Vogt 

 and Jung ('88-'89) have described algae in the crinoids. 

 De Negri (76) claimed that Elysia viridis, a mollusc, con- 

 tains real chlorophyl. Brandt investigated this form, and 

 found symbiotic algae present in the contractile canal 

 system. 



In the land snail, Cyclostoma elegans, there is a peculiar 

 group of cells located between the kidney and the stomach 

 that supposedly functions as a "storage kidney." Mercier 

 ('13) investigated this structure, and demonstrated the 

 presence of bacteria in the cells. In the early stages of 

 development the cells contain no bacteria. A peculiar 

 type of inclusion (like a cyst) develops in the cells, and at 

 the same time bacteria appear in the cytoplasm. The 

 "cyst" contains uric acid and xanthin. It enlarges until 

 there is only a thin layer of cytoplasm around it. The 

 bacteria also increase in number. They vary in morphol- 

 ogy; some are straight rods; others slightly S-shaped, and 

 the remainder are filamentous. Presently, phagocytes 

 wander in amongst the cells and later penetrate them. 

 Vacuoles then develop in the phagocytes and the bacteria 

 can now be seen clumped in the vacuoles, apparently, in a 

 state of digestion. The uric acid cyst dissolves and is 

 absorbed. Mercier found this structure in animals ob- 

 tained from various localities. He was not able to find a 

 mature female with eggs, and consequently was unable to 

 study the manner of transmission of the microsymbionts. 



