16 



MYCETOZOA 



rhythmic flow advances or retreats, but gradually growing with 

 the advancing movement. As the sporangia develop, an 

 envelope, the sporangium-wall, is secreted by the protoplasm 

 at the surface. This is at first of a gelatinous consistency, 

 but ultimately becomes membranous. Simultaneously a 

 system of branching anastomosing threads, the capillitium, 

 is secreted in the interior of the sporangium, forming a 

 network traversing the still homogeneous protoplasm. The 

 basal part of each young sporangium contracts and forms 

 a stalk consisting of a tube of tougher hyaline substance, the 

 continuation of the sporangium- wall, through which the 



protoplasm continues to 

 flow until the surround- 

 ing veins have emptied 

 their contents into the 

 spherical head. The 

 coarse refuse matter 

 which has not been 

 discharged along the 

 track of the Plasmo- 

 dium, where it often 

 takes the form of a 

 hypothallus connecting 

 the sporangia, is de- 

 posited in the centre 

 of the stalk. 



In the genus Physarum 

 the lime- granules which 

 abounded in the Plas- 

 modium are in part 

 incorporated in the 

 wall-substance, and in 

 part deposited within 

 lime-knots or vesicular 

 swellings of the hyaline threads of the capillitium. In 

 Didymium the lime-granules which can be seen in the Plas- 

 modium are dissolved in the sporangium, and the salt in 

 solution passing through the soft sporangium-wall forms into 

 crystals on the outer surface. The various kinds of 

 capillitium represented in the different genera and species 

 are described in the text. In all genera that possess a 

 capillitium, this structure is developed before spore-formation. 

 The formation of spores in the Endosporeae is preceded by 

 the division of the nuclei in the spore-plasm by karyokinesis. 

 The process was first recorded by Strasburger as occurring in 

 the genus Trichia* Recent observations show that this 



Fig. 7. — Comatkicha nigra Schroeter. 



From a stained preparation of a young sporan- 

 gium, showing the spore-plasm separated into 

 rounded masses about groups of nuclei, which 

 are dividing by karyokinesis ; the nuclear division 

 has reached the ' ' spindle stage " ; the spindles are 

 seen in profile in all cases but one in which the 

 equatorial plate is seen from one of the poles of 

 the spindle. Magnified 1200 times. 



Botan. Zeit., xlii. 305 (18S4). 



