422 SECOND PART. — MYCETOZOA. 



without success. Germination lakes place under conditions which will be more 

 particularly related in a subsequent page ; in most species when the spores are 

 placed in water. 



The germinating spore (Fig. 182) swells first of all by absorption of water, and 

 one or two small vacuoles, which disappear and reappear alternately, are seen near the 

 upper surface of the protoplasm in which rotating movements are often observed ; at 

 length, and usually 12-24 hours after the scattering of the spores, the membrane 

 bursts and the protoplasm oozes or creeps slowly out of the opening. The 

 protoplasmic body then either at once, as is the rule, or after a transitory period of 

 rest, during which it assumes a spherical form, commences amoeboid movements, 

 undulating changes of outline and protrusions and withdrawals of pointed processes, 

 and in this way becomes elongated into a body which moves about in the water like 

 a swarm-spore and is known by the name of swarm-cell (F*ig. 182 d-f). 



The swarm-cell has the same structure as the protoplasmic body before it 

 emerged from the spore, only that the granules in the protoplasm are collected together 



in the larger part of the cell, which is the 



A' hinder part in the movement, while the anterior 



A ) part is free from granules and also contains 



/^ . A the nucleus. From one to three vacuoles lie 



: A A? in the posterior part, one of which at least 



"- -W\d ' s known as the contractile vesicle, because 



''■!;' , i - V^J in about a minute's time it grows smaller and 



§T^ disappears, and then reappears and enlarges 



A ' (ttwh *'" ^ * s onc tmr ^ or one ^ ia ^ tne breadth 



j*^ T&is? a> of the protoplasmic body. The granules or 



lumps of mucilage in the spore either continue 



in the swarm-cell, or they are dissolved before 



< the protoplasm leaves the spore, or they are 



A& ™'™or S r™?::n £jri2 extruded and left behind within the membrane. 



ruptured spore-membrane, e an older swarm-cell with r Fl „ ~ ill r. 1 1 



ciiia. ran amoeboid swarm-ccii without .,!,.>. The fine i he swarm-cell has no firm membrane, but 



wart-like dots on the spon-nH-n.l>r.ine such as occur in l ; iir. r ^ y. .• l j . • . • , , 



193* are omitted in the drawing., Magn. 390 times. carelul observation shows that it is surrounded 



by a tolerably broad, pellucid and indistinctly 

 defined envelope of the consistence of mucilage. 



The movements of the swarm-cells are of two kinds : a hopping and an 

 amoeboid creeping movement. 



In the hopping movement the cell floats freely about the water with its anterior 

 extremity usually turned upwards. This extremity is finely pointed, the point being 

 drawn out into a long cilium or flagellum with an undulating and swinging movement; 

 in exceptional cases only there are two cilia. The posterior extremity is usually broad 

 and rounded off, and the presence of a cilium there is quite abnormal. The body 

 thus constituted rotates round its longitudinal axis in the circumference of a cone the 

 apex of which is formed by the posterior extremity. The cilium swings with an 

 undulating motion from side to side, making the swarm-cell move in a similar manner 

 and advance in one direction ; sometimes there is no rotation. The body at the 

 same time exhibits constantly varying undulatory movements of its surface, with bending 

 and contraction and recurrent expansion of the parts. 



