DESMIDIACEA 287 



The fluid is here acting in positive jets, that is, with an 

 almost arterial action ; and according to the strength with 

 which it is acting at the time, the loose floating bodies are 

 propelled to a greater or less distance from the end of the 

 endochrome ; the fluid thus impelled from a centre, and 

 kept in activity by the lateral cilia, causes strong eddies, 

 which give a twisting motion to the free bodies. The 

 line a, in this diagram, denotes the outline of the mem- 

 brane which encloses the endochrome ; on both sides of 

 this cilia may be detected. The circulation exterior to it 

 passes and repasses it in opposite directions, in three or 

 four distinct courses of globules ; these, when they arrive 

 at c, seem to encounter the fluid jetted through an 

 aperture at the apex of the chamber ; which disperses them 

 so much, that they appear to be driven, for the most part, 

 back again on the precise course by which they had 

 arrived. Some, however, do enter the chamber ; occasion- 

 ally, but very rarely, one of the loose bodies may be seen 

 to escape from within, and get into the outer current, it is 

 then carried about until it becomes adherent to the side of 

 the frond. 



With regard to the propagation of the C. Lunula, we 

 have never seen anything like conjugation; but we have 

 repeatedly seen what the reverend gentleman has so well 

 described increase by self-division. 



Observe the diagram D ; but for the moment suppose 

 the two halves of the frond, represented as separate, 

 to just overlap each other. Having watched for some 

 time, the one half may be seen to remain passive ; the 

 other has a motion from side to side, as if moving on an 

 axis at the point of juncture : the separation then becomes 

 more and more evident, the motion more active, until at 

 last with a jerk one segment leaves the other, and they 

 are seen as drawn. It will be observed, that in each 

 segment the endochrome has already a waist ; but there 

 is only one chamber, which is the one belonging to the 

 one extremity of the original entire frond. The globular 

 circulation, for some hours previous to subdivision, and for 

 some few hours afterwards, runs quite round the obtuse 

 end of the endochrome a, by almost imperceptible 

 degrees; from the end of the endochrome symptoms of 



