40 IIOFMEISTER, ON 



developed to the extent of two third parts, and never com- 

 bine to form partition-walls. If there were any need of ad- 

 ditional evidence in opposition to the theory again brought 

 forward by Karsten, viz., that vesicles too small to be seen 

 with the microscope gradually grow into daughter-cells and 

 occupy the entire space of the mother-cell, it would be 

 afforded by the existence for three months before, as well 

 as during and after the individualization of the spore, 

 of a secondary nucleus in each of the protuberances of the 

 mother-cell, which protuberances for a long period freely 

 communicate with one another. The circumstance that 

 the four protuberances of the mother-cell of Pellia, which 

 eventually become the spores, leave a space between them 

 filled only with water, is a convincing proof of the inde- 

 pendent nature of the halves of the primordial utricle. 



The young spore divides by a transverse septum very 

 shortly after it has become clothed with a proper membrane ; 

 usually whilst it remains attached to its three sister-spores 

 by the remnants of the mother-cell (PI. V, figs. 18, 19). 

 Upon the commencement of this process the central nucleus 

 of the spore, disappears ; two new nuclei, of a flattened ellip- 

 soidal form, appear (PI. V, fig. 18). The numerous small 

 chlorophyll-granules through which the nucleus is faintly 

 seen, thereupon appear separated into two groups, each 

 filling one half of the spore, so that in its equator there is 

 formed a narrow zone of transparent mucilaginous fluid, 

 free from granules and chlorophyll -bodies. This light space 

 appears suddenly traversed by a very delicate but sharply 

 defined line, which is the side view of a septum passing 

 through the spore (PL V, fig. 21). The same process is 

 shortly afterwards repeated in each of the two semi-ellip- 

 soidal cells which are thus formed (PL V, figs. 19, 22, 24). 

 At this time (the beginning of December) one of the four 

 middle cells sometimes divides by a longitudinal septum 

 also (PL V, fig. 23). Henceforth the number of the cells 

 of the spore does not increase until its dispersion in the 

 spring of the next following year. The spore, however, 

 secretes over its whole extent a brownish, slightly trans- 

 parent outer membrane, covered on its external surface with 

 numerous very small asperities, which, when the spore is 



