46 The Mycetozoa, and 



A connected system is presented by the capillitium of the 

 beautiful genus Arcyria (Fig. 6). The immature sporan- 

 gium is a long egg-shaped case standing on a pedicel ; as 

 it ripens the upper half or two-thirds of the membrane 

 burst and fall off, leaving the lower part to form a cup (c), 

 from which is seen to arise a thick web of fibres, almost 

 like a pillow made of delicate horsehair (cap). These fibres 

 are elastic, and so soon as the wall of the upper part of 

 the sporangium gives way they expand to a height and 

 breadth greatly in excess of the capsule in which they were 

 contained. There can be little doubt but that these elastic 

 fibres when mature must exert a great upward and outward 

 pressure on the walls of the sporangium, and no doubt 

 they hasten the disappearance of the upper parts of the wall. 



In some species the system of hairs remains attached to the 

 cup, which is the abiding part of the sporangium wall ; in 

 other species it is attached to the interior of the stalk only by 

 a few branches, and then it is apt to fall away from its cup. 



The likeness between the hairs of the sporangia of the 

 genera Trichia and Hemitrichia, and of the Junyermanniss 

 is very close, and the same variety of arrangement is found 

 in both cases. Both families exhibit elaters marked by 

 spiral thickenings (see Fig. 12) ; but in the myxies these 

 thickenings appear to be external, whilst in the Junger- 

 mannise they are generally, or always, internal. Both 

 groups show differences in the number of these spiral 

 thickenings ; they are sometimes single (as in Hemitrichia 

 Wigandii), or double, and sometimes reach to as many as 

 six (in Hemitrichia clavata). In both groups the hairs are 



