1909] CURRENT LITERATURE "I 
animal presently ceases to take food from without, and is nourished entirely by 
its endophytic algae; in the former, the animal continues to feed throughout its 
lifetime. For some reason, the parasitism is less complete. 
The benefit to an animal in association with a plant is much more obvious 
than the benefit accruing to the plant. It is customary among naturalists to con- 
ceive of every structure, every act, every situation, as useful or advantageous to 
the organism, or as having been useful or advantageous in the past. Many cases 
might be cited which stultify such a position, yet KEEBLE seeks to find some value 
to the independent alga in its association with a dependent animal, and believes 
that it consists in a “solution of the nitrogen problem—a successful method of 
obtaining large supplies of nitrogen.” This is plausible, and adding a usable 
nitrogen compound, such as uric acid or potassium nitrate, in due proportions to 
the food-free filtered water of laboratory cultures, prolongs the life and prosperity 
of plant and animal alike. But as Kersze plainly indicates, this profits individ- 
uals, not the species. Ingested algae of a certain sort, escaping digestion and 
manured with animal wastes, multiply in the tissues of this small animal; they 
grow and prosper; but beyond the body of the individual animal they do not appear 
to spread. They do not infect the eggs; they do not escape from the body of 
convoluta before or after its death; they die with it. Each convoluta larva is 
separately and freshly “infected” by some of its food which it fails to digest. But 
although KEEBLE has failed to find the alga in its free form, he believes that it has 
one, and that the species is continued by those individuals which escape the con- 
volutas. Indeed this belief is inevitable, if the ingested and surviving endophytes 
produce no successors. 
I can do no better than quote Krrsre’s own vigorous summary. “The. 
interpretation of the relation between yellow-brown cell and animal depends on 
the point of view: From that of the animal it is obligate parasitism. From 
that of the species ‘infecting organism,’ it is an insignificant episode, involving 
the loss of that, probably small, proportion of its numbers which are 
ingested. From that of the individual ingested yellow-brown cell, it is a solu- 
tion of the nitrogen problem—a successful method of obtaining large supplies 
Of nitrogen. 
' Obviously, then, to the species of alga there is no use in the association; to 
certain individuals, which apparently produce no successors, there may be some 
_ advantage. Even if there were no other, I suppose some persons would claim an 
1 advantage for the algae which escape digestion and survive in the body of the 
: 
animal, on the hypothesis that life is better than death! 
KEEBLE has not yet succeeded in finding the yellow-brown cells in the free 
state, in cultivating them free from the animal body, or in identifying them with 
any now known algae;- yet he has no doubt of their being algae. There is little 
reason either to question his opinion or to doubt his ultimate success in cultivating 
and identifying them. 
eoretical val d interest of this paper is greatly enhanced by the skill 
and care of the author as experimenter, writer, and draftsman.—G. J. PEIRCE. 
