756 MICKOSCOPIC FORMS OF ANIMAL LIFE 



and thoroughness by Messrs. Dallinger and Drysdale, of whose im- 

 portant observations a general summary will now be given. 1 



The present Editor adopts the lead of Dr. Carpenter, in 

 arranging the saprophytic monad forms in this place in the organic 

 series. They possess features that ally them, as has been already 

 suggested, to the vegetable series, and indicate affinities with 

 certain ISTostocacese and the Bacteria. 



There are some reasons for looking at the saprophytic monad 

 forms as a possibly degraded but still specialised group. In common 

 with saprophytic Bacteria, they are specifically related to the setting 

 up and carrying on of decomposition in dead organic tissues. In 

 organic infusions and films of gelatine, or tubes of agar-agar, the 

 bacterial forms are. as a rule, enough to set up and carry 011 the 

 destructive ferment. But whei-e great masses of tissue are decom- 

 posing, the presence of the larger monad forms is certain and in- 

 evitable ; and by them, accompanied by the Bactei'ia, the processes 

 of fermentative rotting are carried to the end. 



It is their morphology which points to the Flagellata, and we 

 should incline to consider them a degenerate, and by degeneration 

 specialised form of the Flagellata if they about eight or nine dis- 

 tinct forms in this latitude belong properly to the Flagellata at 

 all. 



The simplest of the>e organisms is represented in fig. 1, Plate 

 XV. A. It has been named by Saville Kent Jfoiias DnUimjrri. 

 and has by comparison a simple life-history. As it is with the 

 entire group, all is subservient to rapidity of multiplication ; and 

 there are two methods in which this is effected. The first and com- 

 monest is by fission ; fig. 1, A, represents the normal form of the 

 organism. It has a long diameter of about the ^^th of an inch, 

 and has great ease and grace, and relative power of movement. 

 In a certain stage of its history as it swims freely there suddenly 

 appears a constriction across its body, as in fig. -1. This is at once 

 accompanied by an apparent effort of the opposite flagella to pull 

 against each other ; the consequence is a very rapid stretching of 

 a neck of sarcode between two halves of the body, as at fig. o. This 

 becomes longer, as at 4, and attains the length of two flagella as at 

 5. when the two dividing halves approach and mutually dart from 

 each other, snapping the connecting fibre of sarcode in the middle, 

 so that two perfect forms are set free, as in (\ and 7. 



This, in the course of from two to three minutes, is once more 

 begun and carried on in each half successively, so that there is an 

 increase of the form by this means in rapid geometric ratio. 



But this is an exhaustive process vitally, for after a period vary- 

 ing from eight to ten days there always appear in the unaltered 

 and unchanged field of observation normal forms, with a remarkable 

 ditlluent or amoeba-like envelope, as seen in figs, s and '.. A. These 



1 See their successive papers in the Monthly Microsr. Joiirn. vol. x. 187:-!, 

 pp. r,:;, '.Mf. ; \ol. xi. 1874, pp. 7, <>!), 97; vol. xii. 1874, p. 2(51 ; and vol. xiii. 1875, 

 p. lK. r ) ; and I'mrrnl. J!o//. Nr. vol. xxvii. 1878, p. 33*2. But especially for the latest 

 n-ulK with recent objectives, Journ. Roy- Micro. Sor. vol. v. 1885, p. 177 ; vol. vi. 

 !>. I'.):!; vol. vii. p. ISfi ; vol. viii. p. 177. 



