642 Cytologie und Befruchtung. — Descendenz und Hybriden. 



longtemps; il se propose d'en parier dans un certain nombre 

 d'articles, dont voici le premier qui apporte d'abord un resume 

 critique de l'etat actuel de notre connaissance de ce sujet. 



L. Petri. 



Chodat, R., Possibilite physiologique de la double 

 fecondation sur Parnassia palustris. (Bulletin de l'herb. 

 Boissier. [2 ] Tome III. p. 363 — 364.) 



L'auteur decrit un sac embryonnaire de Parnassia palustris 

 dans lequel on peut voir deux oospheres, quatre synergides, 

 trois noyaux polaires et trois antipodes. Apres dlvision du 

 noyau primaire le noyau superieur a donne naissance ä un 

 apparei! normal et ä un noyau polaire; l'inferieur a produit 

 egalement un appareil antipodial normal, mais le noyau polaire 

 en route pour se fusionner avec l'autre s'est divise com.me le 

 noyau original de l'appareil femelle en produisant comme lui 

 deux synergides, un oeuf et un nouveau noyau polaire. L'auteur 

 considere que par leur chromatophilie les noyaux polaires portent 

 un caractere femelle. Chodat (Geneve). 



Pearson, Karl, On Homotyposis in Homologous but 

 difierentiated organs. Mathematical Contribu- 

 tion to the theory of evolution. (Proc. Royal Society. 

 LXXI. 1903. p. 288—314.) 



This paper investigates the corrections to be made to the 

 apparent homotypic correlation. 



I. when the pairs of homologous parts are differentiated 

 from each other by their periods of growth; 



II. when each pair of homotypes is differentiated by a 

 common period of growth from other pairs of homotypes; 



III. when the pairs of homologous parts are differentiated 

 from each other by Situation on the organism. 



I. Is illustrated by considering the relation betvveen head 

 lengths of brothers at different ages in childhood, allowing for 

 the growth the fraternal correlation is found to be in good 

 agreement with the values found for adult measurements. 



The second part of the paper deals with the homotyposis 

 of serial homologous parts, Equisetum arvense being taken as 

 illustration. 



Correlation Tables are given for: 



I. Number of Branches to the whorl and position of whorl. 



II. Number of Branches on any whorl of a plant and 

 number of Branches on any second whorl of the same plant: 



«) for all whorls — here the homotyposis is quite 

 insensible; 



/?) for 3"^, 4"'^ 5*'' whorls — this gives a high homo- 

 typosis; 



y) for the first 10 whorls; 



ö) for whorls from the 2"^' to the 10'^. 



