Cytologie u. Befruchtung. 55 



The binucleate condition is brought about by the migration oi 

 a nucleus from an adjacent cell. All stages of this migration, 

 including its passage through the partition-wall, were seen. 

 Fusion of the two nuclei may take place. In the mitosis 

 following the approximation of the two nuclei a much larger 

 number of chromosomes than that characteristic of the gameto- 

 phyte was observed. The migration of nuclei goes on discon- 

 tinuously in a growing prothallium, and this fact is correlated with 

 the sporadic occurrence of sporophytic members known to occur 

 on such prothallia. The process is regarded as being of the 

 nature of an irregulär fertilisation. j. B. Farmer. 



Hill, A. W., Notes on theHistology of the sieve-tubes 

 of certain Aiigiospenns. (Annais of Botany. XVII. 1903. 

 p. 265—267.) 



The sieve-tubes of Vitis vlnifera , Wistaria chinensls, 

 Cucurbita maxima, Tilla europaea and Viscum album were 

 studied and were found to agree closely with the corresponding 

 structures previously described by the author for Pimis. The 

 slime-strings are large, and each is enclosed in a callus-rod, a 

 group of these constituting a „sieve-field". The callus masses 

 are completely perforated by the slime-strings, and so the 

 adjacent sieve-tube Clements are put into communication with 

 each other. 



The slime-strings originate in groups of much finer (proto- 

 plasmic?) threads which, during the ferment action that leads to 

 the production of callus-rods, are finally converted into the 

 strings, and it would seem from the author's account that these 

 originally separate delicate strings fuse laterally to give rise to 

 the Single slime-string met with in each older callus-rod. The 

 slime-strings themselves form the actual means of communication 

 between the adjacent members of a sieve vessel. The callus is 

 of merely secondary importance. j. B. Farmer. 



LOEB, Jacques, Ona method by which the eggs ofa 

 sea-urchin [Strongylocentrotus purpuratus] can 

 be fertilized with the spermof a star fish [Asterias 

 ochracea]. (University of California Publications; Physiology. 

 1903. Vol. I. p. 1—3.) 



In der vorliegenden Mittheilung giebt Loeb an, dass es 

 ihm gelungen ist, die Eier eines Seeigels (Strongylocen- 

 trotus purpuratus) mit dem Sperma eines Seesternes 

 (Asterias ochracea) zu befruchten, zwei Thiere also mit- 

 einander zu bastardiren, die nicht nur verschiedenen Gattungen, 

 sondern verschiedenen Unterabtheilungen der Echinodermen 

 angehören. Er erreichte es durch die Einwirkung gewisser 

 Lösungen auf die unbefruchteten Eier; in diesen Lösungen tritt 

 keine Parthenogenesis ein^ auch können in ihnen die Eier durch 



