1908 ] 
Recknt Baltimore Meetings 
149 
stances in the egg and obtains larvae with correspondingly mis- 
placed organs. Thus experiment confirms his earlier conclusion. 
In cases like the preceding, differentiation even when inter- 
fered with is not directly affected by external factors but is clearly 
the result of internal agencies. A capital instance, as it would 
seem, of the direct influence of an external agency on the differ- 
entiating embryo was discussed by C. R. Stockard, who finds that 
if the fertilized eggs of the teleost Fundulus are treated with a 
trace of magnesium chloride cyclopean monsters regularly develop 
in considerable number. Another interesting paper dealing with 
vertebrate monsters and the causes of their production was pre- 
sented by H. H. Wilder who sharply separates mere malforma- 
tions from bilaterally symmetrical monsters which develop in an 
orderly fashion, as Wilder thinks, in obedience to a mechanism of 
control inherent in the germ. 
The numerous experiments of recent years on hybridization and 
artificial parthenogenesis in the echinoderms have made it clear 
that before we can deduce with certainty the influence of the two 
sexes in determining the characters of the resultant embryo and 
larva, we must know more about embryonic variability in the 
species experimented upon. D. H. Tennent has made a good 
step in this direction in his mapping out of the embryonic varia- 
bility in the Beaufort echinoids which he has been using for experi- 
mental work. 
A considerable number of papers that would collectively fall 
under the rubric of experimental evolution dealt with phenomena 
of inheritance as disclosed in the breeding of poultry, pigeons, 
rats, and insects. Some of the results fit in very well with the 
hypothesis of unit. characters and Mendelism, but W. L. Tower 
stated that he had been unable to make use of Mendel’s ideas in 
his experiments, since in the offspring from his crossed forms the 
parental characters might or might not appear in the Mendelian 
ratios. C. B. Davenport voiced the widely entertained opinion that 
even in apparently contradictory cases, such as those presented by 
Tower, Mendelism gives a clue that will aid in unravelling the 
tangle of factors. 
Good contributions to systematic zoology and geographical distri- 
bution were not lacking. C. HartMerriam gave an account of the 
