10 A. E. HILTON ON CAPILLITIA OF MYCETOZOA. 



with contents giving the effect of light and dark spaces, alter- 

 nately arranged along the interior of the threads. Whether 

 it is the light or the dark spaces which determine the positions 

 of the future rings is not clear ; but there is little doubt that 

 the rings are formed by the tubes contracting in length and 

 enlarging in diameter in either the dark or the light regions,, 

 the intermediate parts remaining as before. The process appears 

 to be less complex than in other Trichiaceae, rings being simpler 

 than spirals. 



The expanding networks of the capillitia of Arcyria are 

 usually ornamented with half-rings, cogs, spines, and other 

 minute prominences, arranged more or less spirally along the 

 i}hreads of the meshes. These discontinuous markings are 

 doubtless the outcome of processes similar in character, but less 

 uniform in result, to those which produce the more perfect spirals 

 of the Trichiaceae. The sudden expansion of the capillitium 

 as a whole, when the sporangium walls give way, is not due 

 to stretching, but to the straightening of bent and tubular 

 threads of the network. In the developing sporangium, cleavage 

 tracks with many curves traverse the plasm in all directions, 

 the membranous tubes secreted along these channels form a 

 network by frequent anastomoses, and when released the 

 fibrous mass expands by the sudden unbending of hollow and 

 flexible threads, and the consequent enlarging of the meshes 

 of the net. After liberation the capillitium never returns to 

 its former condition, but remains expanded. 



In the genus Lycogala a modification is brought about in a 

 very simple way. The plasmodium of the familiar species 

 Lycogala epidendrum rises from the rotting wood as a cluster of 

 coral-red protuberances which increase in size until they meet 

 and coalesce into an aethalium, i.e. a rounded mass of confluent 

 sporangia. By this coalescence, which occurs while the plasm 

 is in a very fluid condition, air in spaces between the rising 

 iorms becomes entrapped ; and this leads to the production of 

 s, pseudo-capillitium consisting of branching and anastomosing 



