564 Descendenz und Hybriden. 



1. The mean number of floral organs of any one kind, 

 and the mean total of floral organ per flower, differ from race 

 to race. 



2. The variability of each series of floral organs, or of the 

 sum of floral organs, differs from race to race. 



3. There is considerable positive correlation between all 

 the series of floral organs, so far as Variation in number goes. 



4. The mean number of organs of any series diminishes 

 as a rule from the commencement of the flowering season to 

 its close; the rate at which this decrease occurs differs in diffe- 

 rent races. 



5. Certain abnormalities (staminodal petals and lobed petals) 

 are more frequent towards the close of the flowering season. 



K. Pearson. 



DONCASTER, L., Experiments in Hybridisation, with 

 special reference to the Effect of Conditions on 

 Dominance. (Phil. Trans. Roy. Soc. Vol. CXCVI. B. 

 p. 119—173. 1903.) 



This paper records a large series of experiments, in which 

 various species of Echinids were cross-fertilised, the object being 

 to discover the effect of varying conditions, either before or 

 after fertilisation, on the dominance of the characters of one 

 parent over those of the other. The word „dominance" is 

 used to denote prepotency with regard to a single character, 

 or group of characters, as manifested in the hybrid; since the 

 hybrids were only reared to the condition of a pluteus larva, 

 it was impossible to discover whether dominance in the Men- 

 delian sense occurred, or not. 



The greater number of hybrids were between Sphaere- 

 chinus granulär is Q and Strongylocentrolus lividus cf , and 

 the characters studied where those of the larval skeleton. 

 1. The hybrids obtained varied in character, according to the 

 season at which the experiments were made, and a body of 

 evidence is given which goes to show that temperature during 

 development is a chief factor in determining the seasonal diffe- 

 rence. Since temperature acting on the ova and spermatozoa 

 before or during fertilisation gave no certain effect, while two 

 batches of eggs, from the same parents, fertilised together but 

 reared at different temperatures gave different average results, 

 the conclusion is drawn that change of temperature does not 

 affect the dominant or recessive character of the gamete, although 

 it may affect the degree to which the dominant character is 

 manifested in the Zygote. 2. The relative freshness or staleness 

 of the ova and spermatozoa used is stated not to affect 

 the dominance. 3. The degree of dominance, in any of 

 the characters observed, was found to vary considerably from 

 individual to individual, and not to be an absolutely constant 

 property of all individuals of one species. 4. The behaviour 

 of the hybrids showed that in spite of the average similarity 



