246 Transactions of the 



while an additional globule shows itself beside the nucleus as at (/, 

 Fig. 1. The constriction gradually becomes more marked, the 

 whole body elongates, and the nucleus-like bodies separate from 

 each other as in c, d, Fig. 7, while at the same time the flagellum d, 

 Fig. 6, appears to split as in a, h, Fig. 7 ; and this continues until 

 the lesser " nucleus " is on one side of the constriction and the 

 primitive one is on the other, as seen in a, h, Fig.. 8, meantime by 

 means not clearly made out, a small cone of sarcode is pushed out 

 at e, Fig. 7, which lengthens and shortly lashes as a flagellum e, 

 Fig. 8, and the fission rapidly proceeds as in Fig. 9, where a and h 

 have assumed the complete form. They now separate, the single 

 anchoring flagellum d, Fig. 6, having completely divided as seen at 

 c, d, Figs. 9, 10, and immediately on separation each flagellum is 

 anchored, and the phenomenon figured at 1, PI, XLII., com- 

 mences ; the same cycle sf)eedily repeating itself. This, however, 

 is not tlie only method, for less frequently the second beak makes 

 its appearance at the front, as in a, h, PI. XLII., Fig. 2, and the 

 splitting is longitiulinul ; the anchoring flagellum dividing as in 

 f/, h, Fig. 2, and the whole proceeding gradually, as in Fig. 3, c, d, 

 the flagellum splits in exact proportion to the sarcode of the body 

 as seen at i,j; the process of fission completing itself in a manner 

 indistinguishable from the former mode ; e and /, Fig. 4, being 

 complete, with perfect nucleus-like bodies, and the flagella k, I, 

 dividing to the end, so that each monad is free. These modes of 

 fission may continue for days without the slightest material change 

 presenting itself to the most careful scrutiny with the highest 

 powers ; the process of fission occupying in each case six or seven 

 minutes. 



But persistent and continuous observation extending over 

 many weeks enabled us to correlate apparently disconnected phe- 

 nomena, and thus to complete the life cycle. 



For years we had been familiar with a triangular form pos- 

 sessing four flagella swimming with tolerable freedom ; this form 

 now frequently occurred in the field ; whilst the splitting of several 

 apparently nucleated globular masses arrested our attention. 



The aspect of one of the latter is seen at Fig. 1, PI. XLIII. 



This one was watched. The flagella a, h, were moving grace- 

 fully, but the body was fixed. After some time, when observing 

 with Jjj and No. 3 eye-piece, a small cone of sarcode was pushed 

 out at e. This was seen slowly to di\dde as at d, e, Fig. 2, 

 and at the same time a diagonal fine c, a, presented itself, and the 

 two globules d, e, Fig. 1, had taken up a position on opposite sides 

 of this line, as in h, d, Fig. 2. In thirty minutes this was almost 

 complete, as seen in Fig. 3, beaks having foi'med apparently by 

 extrusion of sarcode, and the two flagella c, d, Fig. 3, being 

 nearly perfect, and in something less than fouv minutes they 



