68 FISH- CULTURAL ASSOCIATION. 
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. Brandt, Patrick Geddes and 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 with green palmellaceous cells, which, 
moreover, did not die after the death of their hosts, but con- 
tinued to live, growing and developing within the latter until 
their total evolution proved them to be forms of very simple 
microscopic green alga, such as Palmella, Gla@ocystis, etc., etc. 
My own observations on some green-colored infusorial animals 
have been of so interesting a character that I will here describe 
what I observed in a green bell-animalcule (Vortcella-chloro- 
stigma). Upon investigating their structure, I found that next 
the cuticle or skin in the outer soft layer of their bodies known 
as the ec/osare, at all stages there was a single stratum of green 
corpuscles very evenly or uniformly embedded. In another 
form (Stezzor), as already noticed by Stein, the same superficial 
layer of green corpuscles was observed, reminding one very 
forcibly of the superficial layer of chlorophyll grains observed in 
the cells of some plants, as, for instance, Anacharis. Now, it is 
well known that certain animalcules are at times quite colorless 
and at others quite green; this appears to be the case with 
Ophrydium. In this last case I have a suspicion that vegetable 
‘parasites may be the cause of the green variety, but as for the 
others, Stentor and Vorticella, 1 am not so sure that their green 
forms are so caused. In them the superficial positions of the 
green corpuscles and their behavior toward reagents, leads me 
to think that they must be regarded as integral parts of the crea- 
tures in which they are found. 
A grass-green planarian worm (Convoluta schultzit), found at 
Roscoff by Mr. Geddes, was observed by him to evolve oxygen 
in large amounts, likea plant, and * both chemical and histologi- 
cal observations showed the abundant presence of starch in the 
green cells, and thus these planarians, and presumably, also, 
