IKTEODUCTION. 



5 



plate and an indication of spindle-fibres converging at the poles ; 

 at a later stage the swarm-cell becomes ellipsoid and a constriction 

 appears in the middle. As bipartition proceeds the nuclear plate 

 divides and the two halves sepai'ate, the connecting achromatic 

 fibres being often discernible. The daughter-nuclei at length 

 retreat to the opposite poles of the swarm-cell, which in about a 

 quarter of an hour from the beginning of the process of con- 

 striction is completely divided. A fla^ellum is in a short time 

 produced by each daughter-cell, which then assumes the original 

 form of the parent. After dividing in the manner described, 

 through a period of uncertain duration, they withdraw the 

 flageUum and creep with slow amoeboid movement. When two 

 of them come in contact with each other they may coalesce; 

 others congregate at this point and form a centre to which great 

 numbers converge, and though they may remain distinct for 

 some time, ultimately unite and mingle into one moving mjass, 

 ' the Plasmodium of Oienkowski. 

 There is no doubt that the 

 young Plasmodia exercise a 

 distinct attracting influence 

 on the swarm-cells in their 

 neighbourhood. Many amoe- 

 boid swarm-cells, after re- 

 maining some time near the 

 Plasmodium, contract and form 

 into microcysts, in which state 

 they are enclosed by the Plas- 

 modium and become sur- 

 rounded with vacuoles, where 

 they are gradually digested. 

 Although the fusing swarm- 

 cells thus lose their individu- „ , ,. .^^ ^^ ^ , 



- . , 1 • 1 • p Young plasmoaimn, with attendant amoeboid 



allty, tneir nuclei, so tar as swaim-cells, some of whicli have turned into 



Vins bpp-n nlraprvBfl rpTnain JnicooyBts (m) : one miorocyst is being digested 



nas oeen ODServea, remain „ a vaouole W. An empty spore-shell is shown 



distinct. For example, eight »*«■ 

 swarm-cells m^y be counted Magnified 470 times. 

 uniting and forming- a Plas- 

 modium, and their eight nuclei can be afterwards distinguished ; 

 but when this number is exceeded the movements of the Plas- 

 modium and the inconspicuous nature of the nuclei present 

 difficulties in the way of their recognition. Whatever reason 

 there may be from general considerations to regard this fusion 

 of individuals as akin to conjugation, no fusion of nuclei, which 

 appears to be an essential part of the process, has yet been 

 obgerved. 



In the Uxosporece represented by the single genus Ceratiomyxa, 

 the spore is ellipsoid, and consists of granular protoplasm, in 

 which four nucleus-like bodies can often be Observed. This is 

 enclosed by a membranous and colourless spore-wall. On placing 

 the perfectly matured Spores in pure water, the membranous 



Fig. 3. — Didtmitjm diffoeme Duby. 



