96 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the impregnation of the tricliogync and formation of the cystocarp 

 could not be followed out. After some time the gelatine disappears, 

 and the filaments are carried away in the current of water. 



Plurality of Nuclei in the Siphoneae.* — G. Berthold confirms 

 the observations of Schmitz f relative to the presence of a number of 

 nuclei in the cells of several Siphoneaj belonging to the genera Co- 

 dium, Derhesia, and Bryopsis. In Codium he has been able to follow the 

 process of division of the nucleus. It first assumes a fusiform shape, 

 then becomes constricted in the middle, while the ends swell out, and 

 finally separate as the two daughter-nuclei, the threads which 

 separated them becoming ruptured and disappearing. In Derhesia 

 there are a number of nuclei in the young sporangia, united to one 

 another by a network of threads. As development advances these are 

 replaced by a much smaller number of larger nuclei, which are at first 

 not sharply defined ; round each of these a zoospore is then formed. 



Conjugation of Zoospores in Dasycladus.| — The discovery by 

 de Bary and Strasburger of the conjugation of zoospores in Acetabu- 

 laria mediterranea induced G. Berthold carefully to examine with the 

 same object Dasycladus clavceformis, which fructifies abundantly in 

 the Bay of Baise. 



The large spherical sporangia stand singly at the apex of the 

 verticillate branches, surrounded by the branchlets of the second 

 order. They are attached to the branch by a short slender pedicel, 

 through which the protoplasm enters the fructifying plant, so that the 

 latter is almost colourless, with the exception of a great number of 

 dark green dots. When all the protoplasm has entered the fertile part, 

 the opening of the pedicel is shut off by a brown septum. The proto- 

 plasm forms in the sporangium a thick opaque parietal layer, which 

 breaks up into the separate zoospores. These escape through a crevice, 

 and immediately move about actively in the surrounding water ; 

 accompanying them are a number of granular bodies, and the peculiar 

 yellowish-brown colouring matter of Dasycladus. The zoospores have 

 a greatly flattened and heart-shaped form. Two long cilia are attached 

 to a short protuberance in the centre of the anterior broader side. 

 They have a clear space or nucleus but no pigment-spot. In the 

 vegetative plant are a large number of nuclei. 



Zoospores from the same plant showed no disposition whatever to 

 conjugate ; but as soon as those from different plants were brought 

 together conjugation took place at once, showing that they are true 

 zygospheres (gametes of Strasburger). A number however remained 

 without conjugating, and soon perished ; while in a few cases an 

 aggregation of a number was observed, as in Acetahularia. The con- 

 jugation takes place by the union of the flat or also of the narrow 

 sides, the coalescence commencing in the middle, and advancing then 

 in both directions. During and after conjugation the zygospheres 



* MT. Zool. Stat. Neapel, ii. (1880) pp. 72-8. See Bot. Ztg., xxxviii. (1880) 

 p. 701. 



t See this Journal, iii. (1880) p. 493. 



$ Gottingen Nachr., 1880. See Bot. Ztg., xxxviii. (1880) p. 648. 



