PROFESSOR W. C. WILLIAMSON ON VOLVOX GLOBATOR. 327 



to be the case when the cell-walls had been torn across ; but 

 after a while many of the cell-walls appear to become bo 

 far softened as to allow the cell-contents to float out. When 

 this is the case, the latter objects invariably pass into the 

 interior of the Volvox. They never appear to break through 

 the outer wall. On examining the cell-contents, after they 

 have thus made their escape, we find that they have under- 

 gone no change beyond that of external form: their com- 

 position is the same as when seen in situ, according to the 

 degree of development which the individual under examina- 

 tion has imdergone. When thus liberated, they exhibit 

 no traces of the two ciliae or **proboscides" of Ehrenberg, and 

 which he describes as belonging to the individual ** animaU 

 cule," and being merely projected through the investing 

 membrane. Neither have we any thing resembling the 

 oral aperture, or sacculated stomachs, delineated in his 

 figure. Indeed, the whole appears exactly like the ordinary 

 cell of an Ulva, deprived of its external cell-wall. 



On turning our attention to the external membrane, 

 from the under surface of which these objects have escaped, 

 we find that the cilias have been left behind, and are im- 

 planted in pairs upon its surface, in a very regular order 

 {Fig. 6). We observe a series of small specks arranged in 

 pairs, and which preserve a degree of relative parallelism 

 (6 a) ; from each of these points a long cilia is projected. 

 It has already been remarked, that when the cell-contents 

 have escaped from a ruptured cell, the vesicle is frequently 

 retained in connection with the latter, by means of a deli- 

 cate ductile thread (Fig. 4 e). In this case the thread 

 always terminates at one or both of these small specks, in- 

 dicating a more intimate union between the cell and its 

 contents at these points than at any other. It is not easy 

 to say what these specks are. They do not appear to be 

 merely minute apertures, since they exhibit a power of 

 condensing transmitted light. 



