INTRODUCTION. 



13 



formed. The chromatin constituents of the nucleus first show a 

 coarser arrangement, which is followed by the " spindle stage," 

 exhibiting an equatorial plate with achromatic fibres converging 

 at the poles. In Badhamia, Physa/nim, Graterivm, Didymium, 

 Steinonitis, Lamproderma, and Comatricha the plasma at this 

 period breaks up into lobed masses containing six to ten nuclei ; 

 the equatorial plate of each nuclear spindle now divides horizontally, 

 and as the two halves draw apart the lobed masses of plasma 

 undergo a further division, untU the time when the daughter- 

 nuclei have widely separated. Though stUl connected by achro- 

 matic^ fibres, each pair is enclosed in a portion of plasma of the 

 capacity of two spores; these portions become constricted into 

 the ultimate spores, each containing a single nucleus : in a short 

 time the spore wall is acquired, and the active stage of the 

 organism comes to a close. In the genera just mentioned, spore- 

 formation occurs in warm weather about twenty hours after 

 the sporangia have taken 

 form. In Trichia tHe in- 

 terval is much longer, ex- 

 tending from two to four 

 days according to the tem- 

 perature. In this genus and 

 also in Arcyria, Lycogala, 

 and Reticula/ria Lycoperdon, 

 the spore-plasm is not seen 

 to separate in lobed masses 

 at the time when the 

 nuclear spindle is formed, 

 but the karyokinetic pro- 

 cess is completed and the 

 daughter - nuclei are de- 



finitplv nartpd frnm otih ^""^ * stained preparation o£ a young spor- 



nniieiy partea irom one anglum, showing the plaamodium separated into 



another before the plasma masses of two spores' capacity round the nuclei, 



1 1 _ J i 1 which have almost diTided by karyokinesiSi 



breaks up and encloses each Magnified 1200 times. 

 nucleus in a young spore.* 



The sporophores of Ceratiomyxa are columnar, or confluent and 

 interlacing. In their early stage the protoplasmic matter spreads 

 throughout the superficial part of the columns, and also in 

 numerous veins traversing the watery gelatinous interior sub- 

 stance. . These veins are ultimately withdrawn to the outer layer, 

 which divides into polyhedral portions of equal size, giving an 

 areolated structure to the even periphery ; each portion contains 

 a single nucleus 2'5 fx. in diameter. The whole sporophore is 

 invested by a thin hyaline layer. The material of this investing 

 layer and the interior gelatinous substance take a bright red 

 colour in preparations stained in picrocarmine, which contrasts 

 with the yellow tint of the protoplasmic matter. The contents of 



* Nuclear division is observed by taking stainings, at short intervals, of 

 the contents of groups of sporangia which have risen together at one time ; 

 further details are given in Linn. 80c. Journ., vol, xxix., p. 629. 



Fig. 8.— Comatkioha cetosata Preuss. 



