474 
written 150 years ago from Mauritius, is of deep interest, for 
not only did he foresee the possible economic use that could be 
made of introducing birds and other animals into Mauritius, but 
he also clearly recognized the principle of the balance of nature 
or the struggle for existence. 
““Tt is a misfortune that we have not here any of those birds which 
destroy insect life. It is only this island that affords the spectacle of 
great forests without a single woodpecker. That is the great enemy of 
white ants, other ants, large and small caterpillars. What a service one 
would render the colony if one could but introduce robins, flycatchers, mag- 
pies, shrikes . . . and other insectivorous birds which never touch grain. 
‘«Small hawks, owls, ete., could be imported to keep check on the multi- 
plication of the smaller grain-eating birds; as well as snakes of a non- 
poisonous kind to destroy the rats. It would even be useful to bring frogs 
to purify the fresh-water pools, ete., of the swarming multitude of gnat- 
larvae which abound in them.’’ * 
This is a remarkable passage, and opens up a lot of interest- 
ing reflections as to where Commerson would have ended had 
he not died a comparatively young man, a martyr to his zeal for 
scientific research. 
But it is not upon these subjects, interesting as they are, that 
I wish to speak today, but upon the very different one of: 
HoMoPpLasMyY** OR CONVERGENT DEVELOPMENT IN 
EvoLUurtIOoN. 
This subject has formed the theme of many works, but I 
shall not touch upon its historic or bibliographic side, but I shall 
simply bring before your notice a few examples to show its uni- 
versality in the animal world and suggest some of its bearings 
upon evolution. 
In both the Protozoa and the Metazoa we find the same 
fundamental types of symmetry, 1. e., radial, bilateral, spiral, 
leiotropic, dexiotropic, and modifications of these.‘ There are 

* Life of Philibert Commerson, Pasfield Oliver (1909). 
** Webster defines this word as: Resemblance between different plants 
and animals, in external shape, in general habits, or in particular organs, 
which is not due to descent from a common ancestor, but to similar sur- 
rounding circumstances. 
+ Kofoid, Nature, August 13, 1923, p. 253. 
