CH.VIII. MORPHOLOGY AND COURSE OF DEVELOPMENT. MYXOMFCETES. 439 



columella ; the slenderer branches resemble those of Didymium and Diachea. The 

 wall of the sporangium is a simple and usually very delicate membrane, and like -all 

 other parts is free from deposits of calcium carbonate. 



The capillitia which have now been described, though of many and apparently 

 very different kinds, must nevertheless from the data before us be all regarded as 

 peculiar membranous or parietal formations secreted or excreted from the protoplasm. 

 Their material composition is not accurately known and will be briefly noticed again 

 in the sequel, but it would appear to be not essentially different from that of the 

 thicker portions of the outer wall of the sporangium to which they are sometimes 

 attached. In the Calcareae (Physarum, Didymium, &c.) their substance or wall passes 

 continuously into the wall of the sporangium of which they appear simply as processes, 

 and thus closely resemble the branching bands of cellulose which spring from the 

 outer wall of a cell of Canlerpa and stretch into the interior of the cell. That they 

 are at the same time quite or partially hollow and take up excreted matter into their 

 cavity, especially into the calcium carbonate-vesicles before described, is in favour of 

 this conception. The wall-processes accordingly serve partly as supports partly as 

 receptacles of the excreta. All that is known of their development (see page 431) is 

 likewise in harmony with this view, which finds important support in Strasburger's 

 recent observation that the development of the capillitium is essentially the same in 

 Trichia as in the Physareae, though the tubes in the latter lie free and with a blind 

 termination in the spore-plasm or between the spores, and are so like some vegetable 

 cells that they were long taken for cells. According to Strasburger the tubes of the 

 capillitium of Trichia fallax are formed by secretion of a membrane from the 

 round spaces in the protoplasm which are of the same shape as the tubes, and are 

 filled with a fluid (?) and have no nucleus. This would not prevent their also serving 

 as receptacles of any excreta. What is true of Trichia may certainly be assumed of 

 Arcyria and the species allied to it. The exceptional features in the Stemoniteae 

 require therefore no further discussion. 



2. The structure of the aethalium in the mature state has been sufficiently 

 explained in the description of the history of the development of the most common 

 form Fuligo varians, the Aethalium septicum of authors, which will be found on 

 page 431. The body, which has the shape of a cake or cushion, is covered with a 

 brittle rind some millimeters in thickness, which is at first of a golden yellow colour 

 but afterwards becomes pale or cinnamon-coloured, and is continued all round the 

 margin into a membranous expansion lying on the substratum. This rind consists of 

 portions of the combined plasmodia which have collapsed and retain only the calcium 

 carbonate and pigment ; within it is a dark-gray mass finely speckled with yellow 

 and readily crumbling to powder, and formed of a fine net-work of tubes, which 

 may be nearly i mm, in thickness and which have exactly the same structure as 

 the capillitium of the sporangium of Physarum. 



Other aethalia are connected by their structure with Didymium, Diachea, 

 Licea, &c., as Fuligo is with Physarum ; but some like Reticularia umbrina require 

 further examination. 



The round sessile aethalia of Lycogala epidendron, Fr., which are as large as a 

 pea or hazel-nut, have a very peculiar structure. They resemble small sporophores 

 of the Lycoperdaceae. Their surface is covered by a paper-like membrane or rind 



