CH.VIII. — MORPHOLOGY AND COURSE OF DEVELOPMENT. — MYXOMFCETES. 433 



these movements the branches of the plasmodia all change their previous distribution 

 through the whole of the thickness of the body and creep to the periphery, where they 

 form a net-work stretching only in the direction of the surface and formed of threads 

 which become successively broader and meshes growing narrower and narrower 

 (Fig. 188 a). The whole is covered on the outside by a thin layer of the hyaline 

 protoplasm which alone forms the whole of the inner portion of the body. When 

 these processes are completed, the net-work of protoplasm breaks up simultaneously 

 into numerous polyhedral portions of nearly uniform size (Fig. 188 b). They contain 

 each a nucleus, become flattened from without inwards, and remain grouped in a 

 simple layer which follows the surface like an epithelium. Then each of these proto- 

 plasmatic bodies begins at once to grow convex towards the outside, and to lengthen 

 out at right angles to the surface of the whole body into the shape of a sphere borne 

 on a slender conical stalk (Fig. 188 b). A delicate membrane is formed at the 



same time within which all 

 the protoplasm passes through 

 the stalk into the spherical 

 expansion at the extremity. 

 The latter then becomes in- 

 vested all round with a some- 

 what thicker membrane with 

 an ellipsoid outline, and thus 

 becomes a mature spore which 

 is readily detached from the 

 empty^hyaline stalk. The entire 

 gelatinous sporophore under- 

 goes no further changes, but 

 in most cases soon dissolves 

 and disappears. 



The other known ecto- 

 sporous Myxomycete,Ceratium 

 porioides, is distinguished from 

 the species just described only 

 by the yellow colour and by 



the shape of its sporophore, which resembles in form the hymenium of a Polyporus 

 (see page 288). 



The development of the sporophores and receptacles as just described runs its 

 course rapidly if the conditions are favourable. According to a series of observations 

 on spontaneously developed Physareae, species of Trichia, Stemonitis and others, the 

 complete development from the commencement of the formation to maturity requires 

 an interval on the average of about 1 2 hours ; the development is quicker or slower in 

 particular species, or according to the temperature and moisture of the environment. 



The sporophores of Ceratium are perfectly formed according to Famintzin 

 and Woronin in the course of a summer night. The entire development of the 

 species may also be accomplished very rapidly. Cienkowski obtained in four days 

 fully formed plasmodia of Chondrioderma difforme when grown on microscopic 

 slides, and these formed sporangia on the fifth day. 



[4] F f 



FIG. 188. a Ceratium kyd?toides Piece of a sporophore in the act of forming : 

 the branches of the Plasmodium in the upper part are already beginning' to be 

 arranged into a dense peripheral net-work, b Ceratium porioides. Piece of the 

 margin of a sporophore, in the beginning of spore-formation ; to the right two spores, 

 which subsequently become slightly ellipsoid, on their stalks. After Famintzin anil 

 Woronin. a magn. about 68 times, b 120 times. 



