Timhcrlahe — Swarm-Spores of Hydrodictyon. 491 



be noted that Braiin failed to distinguish the nuclei as such. It 

 is quite probable, of course, that the light spots that he speaks 

 of were the nuclei, but it would be hard to always distinguish 

 them in living material. 



In material fixed in alcohol and stained with haematoxyline, 

 Strasburger (23) was able to distinguish, in the protoplasmic 

 layer of the cell, numerous small nuclei which he thought di- 

 vided just prior to cleavage. Strasburger bases his account 

 of the rest of the process of cleavage entirely upon the obser- 

 vations of Braun and Cohn (5) as tlieir descriptions agreed 

 well v.'ith his account of simultaneous cleavage in many other 

 coenocytic cells of the Algae and Fungi. 



In 1890 Artari (2) attacked the special problem of the sig- 

 nificance of the nuclei in the process of cleavage and also gave 

 considerable attention to the structure of the chromatophore. 

 He thouaiit that the chroma toT)hore is in the vounsr cell an irre^- 

 ular plate like body with long projections similar to the chro- 

 matophore of Drapar?ialdia. During the growth of the cell 

 the projections bend over and fuse so as to form a net which 

 by increase in extent of its parts becomes a perforated plate 

 on the inner side of which the nuclei lie. In material fixed 

 in picric acid and mounted in glycerine or Canada balsam 

 Artari was able to make out that each nucleus contained a 

 prominent central nucleole. Farther than this, however, no 

 details of nuclear structure were described. Cleavage begins, 

 according to Artari, by the division of the chromatophore into 

 irregularly hexagonal areas each of which contains a single nu- 

 cleus. These areas are separated by a transparent plasma cor- 

 responding to the light lines of Braun. 



It Vv'ill be seen from the above paragraph that Artari's ac- 

 count of the cleavage process difi'ers in no important particu- 

 lar from that of Strasburger. His description of the develop- 

 ment of a distinct chromatophore is, as I have pointed out in 

 another place, based upon inadequate means of observation, due 

 to his methods of treating the material. The apparent simil- 

 arity of the chromatophores of such a form as Draparnaldid to 

 the chlorophyl containing cytoplasm in the young cells of Hy- 

 drodictyon might easily lead one to the conclusion that chro- 

 5 



