BULLETIN OF THE UNITED STATES FISH COMMISSION. 411 



mutual help in the processes of nutrition and excretion. This singular 

 association and interdependence of the animal host and the vegetable 

 guest has received the somewhat cumbrous name of Symbiosis, which 

 may be translated pretty nearly by the phrase associated existence. 

 This is not the place for the discussion of the purely scientific aspect of 

 this question, as already ably dealt with by Dr. ]>randt, Patrick Geddes, 

 Geza Entz, and others, and we will therefore only notice their researches 

 in so far as they appear to have a bearing upon the origin of the green 

 color of the oyster. Entz has discovered that he could cause colorless 

 infusoria to become green by feeding them with green palmellaceous 

 cells, which, moreover, did not die after the death of their hosts, but 

 contined to live growing and developing within the latter until their total 

 evolution proved them to be forms of very simple microscopic green al- 

 gae, such as Fulmella, Glceocystis, &c. (E. P. Wright). My own obser- 

 vations on some green microscopical animals have been of so interesting 

 a character, that I will here describe what I observed in a green bell- 

 animalcule. Next the cuticle or skin in the outer layer of their bodies, 

 in all stages, a single stratum of green copuscles were found to be uni- 

 formly embedded, like the chlorophyl grains observed as a superficial 

 layer in the cells of some plants — as in Anacliaris, for example. The same 

 arraugement of the green corpuscles had been observed in Stentor, the 

 trumpet- animalcule, many years before, by Stein. There may be para- 

 sites, as observed by Dr. Entz, but, judging from their superficial po- 

 sition, their globular form, and behavior towards reagents, the absence 

 of a nucleus or of any cleavage stages, they must, it seems to me, be 

 regarded as integral parts of the creatures in which they are found. 



A grass-green planarian, Convoluta schultzii, found at Roscotf by Mr. 

 Geddes, was discovered by him to evolve large amounts of oxygen like 

 a plant, and "both chemical and histological observations showed the 

 abundant presence of starch in the green cells, and thus these planari- 

 ans, and presumably, also, Hydra, Spongilla, &c., were proved to be truly 

 vegetating animals." Similar facts have since been observed in rela- 

 tion to other green animals by the same naturalist. 



That the green observed in a number of animal organisms is of the 

 nature of chlorophyl, or leaf green, has been proved by Lankester (see 

 Sach's Text-book of Botany, p. 687), by means of the spectroscope. A. 

 W. Bennett, in alluding to Lankester's observations, says: "In all 

 cases the chlorophyloid substance agrees in having a strong absorption 

 band in the red — a little to the right or left ; and except in Idotea, in 

 being soluble in alcohol, and in having strong red fluorescence, and in 

 finally losing its color Some time after its solution. 



The vegetable organisms which have been found to inhabit the lower 

 forms of life alhided to above have been regarded as belonging to two 

 genera by Dr. Brandt, which he has named ZoocJUorella and ZodxantheUa, 

 and which are probably synonymous with the genus Philozoon pro- 

 posed by Mr. Geddes. But the latter claims to have demonstrated the 



