AMONG SIMPLE SAECODE OE&ANISMS. 425 



body (C). In the mean time the nucleus has become divided into 

 two, and between its halves the fission of the body proceeds 

 until completed, and the two segments are set free. Each of 

 these (D) is as yet provided with only two flagella, which imme- 

 diately begin to split from the free end to the base, and the 

 complete form of the parent monad with its four flagella is thus 

 acquired. The two flagella during this act of splitting are attached 

 to some fixed object by their distal ends and then thrown into a 

 state of rapid vibration. 



Besides the multitude of free-swimming, semiamoeboid indivi- 

 duals thus noticed in the act of self-division, some (E) may be seen 

 in which the amoeboid condition is much more decided on the pos- 

 terior end of the body from which pseudopodia are being constantly 

 protruded, while the anterior end with its four flagella continues 

 with but little change. The nucleus has become much larger. 



In this condition the monad swims more and more slowly until, 

 in some cases, it ceases entirely to swim, and moves about solely 

 by the aid of pseudopodia, exactly like an Amoeha. 



If it now meet another in a similar condition, the amoeboid parts 

 unite and instantly blend into one another (F). This blending 

 together of the two bodies becomes more and more intimate ; the 

 two sets of flagella unite and become fused into the general sar- 

 code, the contractile vacuoles flow together and become inactive, 

 the two nuclei also flow together, and, finally, the blending has 

 become complete ; all trace of the original form is lost, and all 

 that remains is a distended roundish sac (H) which, after the lapse 

 of some hours, will be seen to pour out in all directions, without 

 evident rupture, clouds of excessively minute points which can 

 be clearly defined as oval refringent corpuscles only by means 

 of a maguifying-power of 2500 diameters. These were followed 

 by the aid of a ^ of an inch object-glass, and their development 

 traced into the form of the original conical monad with its four 

 flagella. 



The life-history thus traced in the "calj-cine monad" corre- 

 sponds in all essential points with what the authors observed in 

 the other species which formed the subject of their investigations. 

 Multiplication by fission took place in every species, while a fusion 

 together of two individuals would seem to be in every case a ne- 

 cessary phenomenon in the developmental cycle of the monad. 

 In one form only, instead of inactive sporules of immeasurable 

 minuteness following as a product of this fusion, the blended 



