EXPElilMENTAL HYBRIDISATION. 
331 
To this assertion I must add two remarks : 
(1) The dominant character is not necessarily transmitted 
in its entirety; it may be lessened by a contrary influence. 
An example of this is to be found here in the fact that the 
]iosterior epaulettes are less perfectly developed in hybrids 
than in pure larvae. This statement does not contradict 
Mendel’s law of dominance. It is necessary to remark that 
one is not working on adult individuals' with fully developed 
cliaracters, but on larvae. Now Lang (’08) Inis observed in 
his crossings of Helix that in young hybrids the rate ol 
development of certain characters is less than in pure indi- 
viduals. Moore (’12) remarks and explains the same fact in 
Echinoderm hybrids. 
(2) It would seem necessary to admit that tiie dominant 
characters are variable, that is to say, that if they are 
normally transmitted to hybrids, this may not be the case if 
certain factors vary. The present experiments perhaps give 
us an example of this. Tlie posterior pedicellaria is, in fact 
not always present in the hybrids. Too much importance 
must not, however, be attached to this example, because one 
cannot absolutely determine what relationship exists between 
the posterior pedicellaria of E c hi n us e sc u 1 en t u s or acut u s 
and the posterior spine of E. miliaris ; and we do not know 
enough of the changes wliich occur in these elements in the 
pure larvae. Better examples of the variability of the 
dominant characters are to be found in the researches on 
ecliinoderm hybrids, whicli have been already jiublished. 
According to Tennent (’10) the heredity of the characters 
varies with the alkalinity of the water. According to Vernon 
(’00), Steinbriick (’02), Doncaster (’04), and Herbst 
(’OG, ’07), this heredity varies witli the seasons or more 
probably with the temperature. It seems, therefore, that one 
may take it that a normally dominant character is weakened 
undei' certain conditions and that a recessive character may, 
under certain conditions, be strengthened and be transmitted 
as a dominant character. 
We should like to compare our results and conclu.sions with 
