274 A. EARLAND ON RADIOLARIA. 



that these yellow cells invariably contained starch, a vegetable 

 product thus apparently arising from an animal source. 



In 1871 Cienkowski published the result of some remarkable 

 observations which explained this seeming discrepancy, the for- 

 mation of starch by an animal organism, and at the same time 

 destroyed the theory of the multicellular structure of the Eadio- 

 laria. He showed that the yellow cells did not perish at the 

 death of the Radiolarian body, but that they continued to flourish, 

 dividing and increasing uninterruptedly. From this fact, coupled 

 with their undoubted cellular nature, he came to the conclusion 

 that they were not integral parts of the Radiolarian organism, 

 but independent unicellular Algae living parasitically in the body 

 of the Radiolarian. 



In 1881 and 1882 Brandt and Geddes published almost simul- 

 taneously the result of further investigations, which proved the 

 accuracy of Cienkowski's theory of their vegetable origin. Brandt 

 found that the yellow cells could survive for some months after 

 the Radiolarian's death, and described them as unicellular alg^e 

 under the name of Zooxanthella, comparing their relations with 

 the Radiolarian organism to the symbiosis between the algoid 

 gonidia and the fungoid hyphse in the Lichens, which had been 

 recently discovered by Schwendener. Brandt also succeeded in 

 removing the xanthellse from living Radiolaria, and in culti- 

 vating them artificially. He then successfully implanted them 

 in the body of a fresh host. Geddes also described the yellow 

 cells as unicellular algse, under the name of Philozoon, and proved 

 by experiment that they give out oxygen under the action of 

 sunlight. Thus, if two Radiolarian colonies of equal size be 

 placed in equal quantities of filtered sea-water in sealed tubes, 

 and one tube be exposed to light while the other is kept in the 

 dark, the latter perishes almost at once, while the former thrives 

 for a long time, the yellow cells absorbing the carbon dioxide 

 expired by the minimal and furnishing in return under the stimulus 

 of sunlight sufficient oxygen for the animal's respiration. 



There is, therefore, no longer room for doubt that the xanthellse 

 are not integral parts of the Radiolarian animal, but separate 

 organisms of vegetable nature, either penetrating actively into 

 the Radiolarian from without, or absorbed passively by means of 

 the pseudopodia. This commensal life must be of advantage for 

 both the symbiontes, for the animal Radiolarian cell furnishes 



