of Sphfcroplea annulina. 93 



viewed as a family of cells (cell-stock). The history of develop- 

 ment here narrated reveals to lis the fact, that, contrary to what 

 has been hitherto imagined in unicellular ])]ants, the individual 

 is not immediately rc])resentcd by each cell, but that these ap- 

 parently equivalent cells become sexually differenced in exactly 

 the same way as is the case in any of the most complicated 

 animal or vegetable organisms ; that consequently each individual 

 cell is by itself barren, and can only be rendered capable of 

 pro])agation by the cooperation of a cell of the other sex. We 

 must therefore distinguish in the cells of the Spha'roj^Iea-f\\di~ 

 ment, male and female cells, or, for comparison with analogous 

 organs in another kingdom of nature, sperm-vesicles and ovaries, 

 which however must be more correctly conceived as inde- 

 pendent, sexualized, elementary organisms. The process of im- 

 pregnation in the Alga has been found precisely similar in the 

 three cases as yet known ; in the Fucaceae, Vaucheria, and Sphce- 

 roplea, the spermatozoids come into immediate contact with pri- 

 mordial cells destitute of (cellulose) membranes. The case of 

 Uphceroplea is especially interesting, because there can be no 

 question here of an accidental contact of the seminal elements ; 

 for if in Fucus the spores to be fertilized emerge upon the sur- 

 face of the thallus — in Vaucheria the surfaces of the antheridia 

 and sporangia come almost into immediate contact — in Sphceroplea 

 the spermatozoids must often make their way through the water 

 to an often far-distant mature female cell, and force an entrance 

 through a narrow orifice. Easy as it is to observe the fact of 

 the entrance of the sperm atozoid, the force which guides these 

 corpuscles through the wide surface of water and the crowd of 

 countless animalcules and plants, to the female cells, and often 

 makes them find their way through the narrow holes at the first 

 attempt, remains still an enigma. I may also recall the fact 

 that Sphaeroplea is as far removed from alliance with Vaucheria 

 as the latter from Fucus, and that since sexuality has been dis- 

 covered in such diverse forms of the Algce, there can scarcely be 

 a doubt that it must only remain to be discovered in the rest of 

 the Algse, and indeed in all plants ; I therefore cannot hesitate 

 to give my adhesion to this conclusion of Pringsheim. 



Whether the remarkable fact, that the spores of Sp/iaroplea 

 do not always give origin, like all other spores and seeds, to one 

 individual, but mostly to several swarming-cells, and therefore 

 to several germ-plants ; — whether this is connected with the 

 action of one or more spermatozoids upon the nascent spore, I 

 must leave unaswered ; the only analogy to this fact is afforded 

 by the origin of several embryos in the ova of the Planarire. It 

 is remarkable, that, according to Pringsheim's discovery, the fer- 

 tilized spores of Vaucheria grow out into a germinal tube by 



