212 SECTIONAL ADDRESSES. 
at intervals, in response to a stimulus, from two kinds of gland cells, 
the secretions, when mixed, producing light. 
Portier’s Hypothesis. 
The numerous cases in which symbiosis occurs in nature have 
naturally led some biologists to ask if symbiosis is not a phenomenon 
of general significance, and perhaps essential, in living organisms. In 
this connection reference must be made to the hypothesis advanced by 
Portier (1918), because it formulates extreme views. Starting from 
his studies of symbionts of leaf-mining caterpillars (Nepticula) and 
wood-devouring insect larve (Cossus, Sesia, &c.), he sought to verify 
the work of Galippe (1891-1918) on micro-organisms occurring in verte- 
brate tissues. Using methods he supposed to be adequate, Portier 
claimed that he could isolate various micro-organisms from vertebrate 
tissues. On faulty premises he built up an hypothesis that may be 
likened to a house of cards. He divides living organisms into two groups, 
autotrophic (bacteria only) and heterotrophic (all plants and animals), 
according as they are provided or not with symbionts. Whereas some 
symbionts are cultivatable, others have become so domesticated in 
respect to their hosts that they cannot be separated from them. The 
essential function of symbionts is to elaborate reserve substances so 
that they become assimilable to the host cell. The mitochondria that 
are present in all plant and animal cells, though not cultivatable, are, 
according to Portier, nothing but symbionts, the importance of their 
function having recently been revealed by Guillermond, Dubreuil, and 
others.? They are derived from food, and, if absent therefrom, illness 
supervenes, as shown by the bad effects of sterilised food, decorticated 
rice, &c., causing deficiency diseases attributed to lack of vitamines, 
which, according to Portier, are nothing but symbionts. Where, as in 
Aphis, the animal feeds on plant sap that is filtered through a tube 
formed by the insect’s saliva—in other words, the insect imbibing food 
devoid of symbionts—the animal is of necessity provided with its own 
well-developed store of them. Portier applies his hypothesis to such 
varied problems as fecundation, parthenogenesis, tumor-formation, 
variation, and origin of species, in all of which mitochondria, that is, 
his supposed symbionts, play a part. His views aroused great con- 
troversy in France, so much so that it was thought necessary for the 
Société de Biologie de Paris (see C.R. Soc. Biol. LXXXITI., 654, 
May 8, 1920) to have a Committee examine the evidence. The Com- 
mittee, consisting on the one part of Portier and Bierry, and on the 
other of Martin and Marchoux (Institut Pasteur), by its report indicates 
the pitfalls, well known to bacteriologists, into which Portier was led, 
and thus disposes of the greater part of his far-reaching hypothesis. 
Nevertheless, like many exploded hypotheses, that of Portier has served 
a useful purpose through the discussion it has provoked and the interest 
in the subject of symbiosis which it has stimulated. 
2 Guillermond has shown that the mitochondria of the epidermal cells in 
Iris elaborates amyloplast and finally starch. Dubreuil (1913) found that 
mitochondria elaborate the fat in fat-cells. Other cytologists have shown that 
glandular secretions are similarly referable to mitochondria. 
