108 Mr. H. J. Carter on the Development of Gonidia 



circulation of the mucus-layer itself is hardly more remarkable 

 than the rapidity with which the green disks are whirled round 

 upon their short axis horizontally or vertically, when they get 

 into the abdominal mucus of one of these vesicles. If this 

 explanation of it meet with disbelief, I can only repeat in its 

 support, that the irregular bodies are similarly affected when 

 they get into this position, though not to such a degree of 

 rapidity, probably from their greater weight and ragged form 

 (fig. 18), and that neither these nor the green disks exhibit this 

 phsenomenon when lying outside the vesicles ; while the rotation 

 of food, when it gets into the abdominal mucus, is a common 

 occurrence in many of the Infusoria, especially in Vorticella, 

 Paramecium, &c. 



We now come to an important point of elucidation ; viz. if the 

 globular vesicle can enclose the green disks so rapidly when a 

 few only of the latter are displaced, they should be able to enclose 

 a far greater number when the whole of the ffreen layer is broken 

 up (figs. 19, 20). Hence it becomes much more likely that 

 this should take place when the so-called " gonidial cells " are 

 formed in the internode (fig. 21), than that portions of the 

 loose mucus, as I had before supposed (p, 7), should wrap up 

 certain numbers of the green disks respectively in their substance, 

 and then pass into closed, transparent sacs or cell- walls. Led 

 on from fact to fact, then, to this conclusion, we now see that 

 the so-called " gonidial sac " is not a new formation, but a pre- 

 existing " globular vesicle,^^ which, when filled with green disks, 

 is in an efficient state, as regards nourishment, to multiply itself 

 by segmentation (fig. 22). That segmentation is the way in 

 which the litter of monads is produced, would appear, first, from 

 the cell-wall losing all power of motion, and apparently life 

 (fig. 20) ; then the formation sometimes (probably always) of a 

 secondary more delicate cell or coat within (fig. 21) ; afterwards 

 a separation en masse of the granules and mucus from the brown 

 or nutritive matter, now become effete (fig. 23) ; and, lastly, by 

 the division of this into the litter of monads (figs. 24, 25). 

 "Whereas, in the propagation by ovules in the Amoebous cells, all 

 foreign matter appears to be thrown off, and the ovules fully 

 formed and separate previous to encystment and incubation. 

 After the monads, formerly called *' gonidia,^' have been deve- 

 loped, the inner cell disappears, and the outer one giving way 

 from decay (?), they escape into the water (figs. 26, 27). 



It is not always that this process can be so distinctly seen, 

 because the brown matter seems sometimes to be so mixed up 

 with the granules and mucus, that the monads appear to come 

 directly out of the former, without a previous separation of the 

 latter. 



