510 Wisconsin Academy of Sciences, Arts, and Letters. 



brane. (Fig. 38.) It is not impossible that the basal bodj 

 is the granule' previously described, that lies against the cleav- 

 age furrow near the nucleus in the latest stages of cleavage ; 

 but I could not find such a body during the stage's of separa- 

 tion and rounding up of the spores. 



The threads connecting the basal body with the nucleus 

 sre very fine and are not always easy to distinguish from the 

 surrounding cytoplasm ; but in most cases they are clearly 

 enough differentiated to enable one to trace them from one 

 body to the other. Thev are colored in the various staininoj 

 methods used about the same way as the spindle fibres or cilia, 

 and in general appearance resemble very much such struc- 

 tures. There is no evidence, however, that any portion of the 

 spindle- ever remains after nuclear division is complete which 

 could be identified as these threads. At the point where a 

 connecting thread is in contact with the nucleus there is no 

 indication of any distinct body or even a swellinor of the nu- 

 clear membrane. I have sometimes found three such threads 

 quite plainly visible, but in most spores there are only two. 

 I have found no cases in which it was clearly evident that 

 there was but a single thread. 



The cilia appear as single fine threads resembling in stain- 

 ing capacity and structure's the spindle fibres. In spores in 

 which the contour of the basal bodv is clearly distinct from 

 the plasma membrane, the attachment of the cilia to the basal 

 iDody itself can be clearly seen. (Fig. 38.) The points of at- 

 tachment of the two cilia to the basal body may either lie at 

 some distance from each other or they may be in immediate 

 contact. (Figs. 36-39.) As previously indicated, the proto- 

 plasm in the forw^ard end of the spore has in the mature spore a 

 hyaline homogeneous appearance. This fact makes the differ- 

 entiation of the basal bodv and connectino; threads much clearer 

 than it otherwise would be. In the giant swarmspores there is 

 a complete locomotor apparatus consisting of cilia, basal body 

 and connecting threads connected with each nucleus. (Fig. 39.) 



As is well kno^\Ti, the swannsporee of Ilydrodictyon do not 

 normally escape from the cell wall within which they are 

 formed but after swimming about for some time in the cavity 



