412 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



truth of the view that the yellow cells of radiolarians and polypes are 

 algte; secondly, the foundation of the hypothesis of the lichenoid nature 

 of the alliance between algae and animal into a theory of mutual depend- 

 ence; and, thirdly, the transference of that view from the region of 

 probable speculation into that of experimental science. 



Hitherto no one has, apparently, noticed the occurrence of green veg- 

 etable parasites in bivalve moUusks except Professor Leidy, who has 

 kindly permitted me to use the facts observed by him relating to Ano- 

 don, one of our common fresh- water mussels. In this animal he observed 

 what he regards as algous parasites, living within the cells of the tis- 

 sues of the molluscan host, larger than nuclei of the cells of the latter, 

 and lodged in clusters in their paraplasm. These facts, observed a long 

 time since, render it very probable that Professor Leidy was one of the 

 first, if not the first, to notice the intracellular parasitism of a plant in 

 an animal. 



Amongst some oysters which were obtained from England through 

 the kind offices of Messrs. Shaffer and Blackford, in response to a re- 

 quest coming from Professor Baird, certain ones were found which were 

 decidedly green. Of these the French specimens of Ontrea edulis and 

 a singular form labeled " Anglo-Portuguese " had the gills of a greenish 

 hue, and in some of the latter the liver, heart, and mantle was very 

 deeply tinged in certain parts, so much so that I decided to make as 

 critical an examination as my resources could command at the time. 

 Spectroscopic investigations gave only negative results, as it was found 

 impossible to discern any positive evidence of chlorophyl from the spec- 

 trum of light passed through thin preparations of some of the green- 

 tinted portions of oysters, some of which, like those made from the heart, 

 were decidedly green to the naked eye. There was no absorjition noticed 

 at the red and blue ends of the spectrum, such as is observed when the 

 light which enters the slit of the spectroscope first passes through an 

 alcoholic solution of leaf green or chlorophyl. Indeed, the spectrum did 

 not api)ear to be sensibly affected by the substance which causes the 

 coloration of the oyster. No attempt was made to still further test the 

 matter with the use of alcoholic green solutions obtained from affected 

 oysters, as the former were not obtainable with a sufficient depth of 

 color because of the relatively small amount of coloring matter present 

 in the animals. If any of the coloring matter was derived from diatoms 

 the spectrum of phj'coxanthine was also not developed. Unstained 

 preparations of the natural green hue were used in all of these experi- 

 ments. Some unstained balsam preparations of the green portions, 

 especially of the heart, showed that the color, which was at first localized 

 and confined to the green cells, after a while became diffused so as to 

 give the preparation a uniform greenish tinge. This is i)roof of its solu- 

 ble and consequently diffusible nature. 



Finally, in order to see if the color was due to the presence of copper. 

 Prof. H. C. Lewis, of the Academy of Natural Sciences of Philadelphia, 



