494 RECORD OF CURRENT RESEARCHES RELATING TO 



dictyon, and Chcetomorpha, with the one fresh-water genus Cladophora. 

 The same writer now gives the following more exact description of 

 the cell-structure, taking as his type Valonia utricularis. 



The cell-wall is clothed internally with a moderately thin layer 

 of protoplasm, enclosing a large cavity filled with colourless cell- 

 sap. Included in the protoplasm are a number of small, flat, disk- 

 shaped chlorophyll corpuscles, of an irregular form. At the growing 

 apex of the cells, which are always more or less tubular, they are 

 densely aggregated into a dark green layer. Most of the chlorophyll 

 corpuscles contain a single starch-grain. 



The great characteristic of these cells is that, in addition to the 

 chlorophyll grains, they contain a number of nuclei embedded in the 

 layer of chlorophyll, and regularly distributed through it at very 

 equal distances. In the larger cells of Valonia they may number 

 several hundred. 



The division of these nuclei takes place by bipartition in precisely 

 the same way as in the Infusoria and other animals of low organiza- 

 tion. The spherical nucleus assumes an ellipsoidal shape, its 

 substance becoming at the same time less dense. The two extremities 

 gradually increase in density, and the intermediate substance becomes 

 more and more absorbed into the two daughter-nuclei, until they are 

 connected only by a thin thread, which is finally ruptured. 



The zoospores are produced in great numbers from a single 

 cell. The whole of the protoplasm of the cell collects around 

 the numerous nuclei, and then breaks up into a large number of 

 zoospores, each with a single nucleus. This nucleus is preserved 

 during the whole of the "swarming" of the zoospore, and in the uni- 

 cellular germ which results from it, becoming then again multiplied 

 by bipartition. 



The structure above described is uniform in its main features 

 throughout the Siphonocladiaceae ; but the mode of cell-division varies. 

 The size of the two sister-cells is sometimes nearly the same, some- 

 times very unequal ; the angle of the new division-wall with the old 

 one may be either an acute or a right angle, the wall itself may be 

 either straight or curved. 



The Siphonocladiaceje therefore, instead of being, as hitherto sup- 

 posed, devoid of a cell-nucleus, exhibit the only instance at present 

 known in the vegetable world of the occurrence of a large number of 

 nuclei in the same cell.* 



Crystalloids in Marine Alg8e.| — Dr. J. Klein has examined the 

 crystalloids in 20 marine algaa belonging to 12 genera, 6 of the species 

 being green, and 15 belonging to the Floridese ; some were examined 

 in the living, others in the dry state. A strong resemblance existed 

 between all the crystalloids examined. Their physiological function 

 appears to be that of temporary reservoirs of reserve material ; when, 

 under certain circumstances, albuminous substances are formed, a 

 portion sej)arates in the form of crystalloids, afterwards possibly to 

 be utilized in the formation of the spores. This is the case probably 



* ^ce also p. 482. t ' Flora,' Ixiii. (1880) p. OS. 



