192 Transactions of the Society. 



In some instances, as in the case we have considered to-night, 

 the division of the sarcode is simple ; it is, so far as our power to see 

 can carry us, a mere cutting of the sarcode into two independent 

 parts. But to secure the independence of each, the most complex 

 arrangements for the supply of flagella have to he provided. 

 The ease and simplicity with which this is wrought is indeed 

 striking. 



On the other hand, there are forms in which the division itself 

 is a mere equi-partition of the sarcode of the hody, devoid even of a 

 discoverable nucleus, and the pulling out, at the point of division of 

 the organism, of a simple neck of protoplasm into a single fibre 

 making new flagella for the two separated parts. 



This is shown in fig. 1, plate VI., a being the normal form, h 

 the earliest discoverable state tending to fission ; the constriction 

 deepens, and each half by individual activity recedes from the other, 

 as in c, d, pulling out the fibre e, which snaps in the middle and 

 each half goes free. 



But not only have we instances of simplicity and of complexity 

 in the fissional provision of flagella ; but there may be increased 

 complexity in the process by the clean division into two of the 

 nucleus. 



In the form shown in fig. 2, this will be readily seen. 

 a is the adult form of the organism. It can swim freely ; but is 

 usually " anchored " by a " trailing flagellum " h. It has a large 

 hyaline nucleus x. 



The first movement towards fission is a partial division of the 

 front flagellum, as at e; then the sarcode of the body begins to 

 divide as at d, accompanied by a splitting of the upper part of the 

 trailing flagellum d. The incision in the sarcode deepens ; and 

 with this the vivid nucleus x shows an incision in its upper part. 

 Kapidly the two halves of the dividing body are as it were torn 

 from each other, the front flagellum is wholly divided, /, j, h, the 

 trailing flagellum nearly so, as at m, n, o, p, and the nucleus is 

 quite divided : immediately after which the two perfect halves are 

 free. 



This is a complex but exquisitely beautiful fission. 



But there are two of the forms that present almost the same 

 problem of how to accomplish a multiple fission ; and each solves it 

 in an independent manner. Their mode of multiple division is seen 

 in figs. 3 and 4. In fig. 3, a is the simple normal form. It 

 swims for a couple of minutes, then assumes a rounded discoid 

 appearance, and becomes still, as at h, the flagellum c melting into 

 the sarcode, 



A white cross suddenly appears as at d, which is rapidly 

 followed by another at right angles to the first ; then it twists into 



