590 JAMES BURTON ON HYDRODICTYON RETICVLATUM. 



it may be, of some thousands of cells, is formed inside each of the 

 members of the original net, which is reproducing. The process 

 takes place in this way. The pyrenoids disappear and the 

 protoplasm collects round each of the numerous nuclei, these 

 then divide repeatedly, until the whole becomes an enormous 

 number of spherical zoogonidia ; there may be from 7,000 to 

 20,000 of them in a single cell. In this they " swarm," as it is 

 called, i.e. they have a tremulous motion, not moving from 

 place to place to any extent, but just vibrating. There is some 

 uncertainty as to whether the gonidia have cilia ; one account 

 says they have four, most say two, and one account I think 

 it is in Kerner says they are not completely separated from 

 one another, but remain attached by a thread of protoplasm. 

 I do not think this is correct and believe they are actually 

 separate for a time, they then become oval instead of spherical 

 and attach themselves to one another by the ends, and gradually 

 in each mother-cell a complete young one is thus formed. 



In the meantime the mother-cell wall gelatinises, and this goes 

 on so that by the time the young net is complete there is scarcely 

 any of the wall remaining, and soon it is entirely diffused and 

 the young one is set free. Some of the books tell us that a slit 

 is formed in the mother-cell and the young net escapes through 

 that, but I have not seen this occur, and think that the des- 

 cription applies to another circumstance namely, the sexual 

 reproduction. This I have not observed, but stated shortly 

 the method is as follows : A much larger number of minute 

 reproductive bodies than in the previous case is formed. From 

 30,000 to 100,000 of them arise in the parent cell ; each of these 

 gametes has either two or four cilia. They issue from the 

 parent cell through a slit in the wall, enclosed in a vesicle formed 

 from the inner layer of the cell, and, becoming free in the water, 

 conjugate in pairs. The resulting zygospore sinks to the bottom. 

 It may germinate at once, but usually divides into two or four 

 parts which become resting spores they are known from their 

 shape as polyhedra ; after some months they give rise indirectly 

 to small nets, which then give rise to larger ones of the usual 

 character. It may be noticed that there is no true sexuality 

 in the cells or individuals of which the net is formed. Any 

 cell may give rise to either sexual or non-sexual reproduction 

 according to circumstances. Klebs (I think it is) has stated 



