in Eudorina clcgans and Cryptoglena. 239 



cell*. Arrived at this state, which wc shall presently see is that 

 of maturity, we also observe that the posterior part of the enve- 

 lope becomes crenulated, apparently from fiaccidity (fig. 3 f/). 



After this, however, it again presents another phase, which 

 may be called the third or last stage of development. Here 

 each cell again undergoes a rapid du])licative subdivision into 

 sixteen or thii'ty-two cells, which, in the group, assume a more 

 or less oblong figure respectively; and thus the Eudorina' s length 

 is increased to 50-5400ths of an inch. The internal structure 

 now gradually breaks down before the external envelope, when 

 for a short time the groups may be seen swimming about the 

 cavity thus formed, till at last the envelope bursts and they 

 become liberated. What becomes of them afterwards, I can- 

 not state from observation ; but the green cells having been 

 gi'catly reduced in size by the latter subdivisions, it is probable 

 that many of the gi'oups, if they do not form new individuals, 

 sooner or later become disintegrated, and the Eudorina thus 

 eventually perishes f. 



When, however, the process of impregnation takes place, the 

 division stops at the second stage, that is, when the Eudorina 

 consists of thirty-two cells of the largest kind, each of which is 

 about l-1866th of an inch in diameter within its capsule, which 

 is therefore a little larger. The process is as follows : — 



At a certain period after the second stage has become fully 

 developed, the contents of the four anterior cells respectively 

 present lines of duplicative subdivision vthicli radiate from a 

 point in the posterior part of the cell (and this distinguishes 

 this subdivision from that (fig. 1) which took place in the ori- 

 ginal cell from which the Eudorina was derived, and that which 

 takes place in the third or last stage of development just de- 

 sci-ibed, where the lines of fissiparation tend towards the centre 

 of the ellipse or ovoid cell). These lines, which ultimately 

 divide the green contents of the cell into sixty-four portions, 

 where the division stops, necessarily entail (from their radiating 

 from a point and terminating a little beyond the centre of the 

 cell) a pyriform shape on the segments, from whose extremities 

 a mass of cilia may be observed waving in the anterior part of 

 the cell of the parent, while yet her own pair of cilia are in 

 active motion, and her eye-spot still exists in situ on one side of 

 her progeny, — thus showing that the latter may be almost fully 



* It is assumed that the green contents get their cell-wall through in a 

 plastic state, before the segmentation commences, as will be seen here- 

 after. 



t For good illusti-ations of this stage, see Prof. Henfrey's description 

 and plate of Pandorina Morum, Quart. Joum. Microacop. Soc. vol. iv. 

 p. 49, 1856. 



17* 



