Septjsmber 1, 1899.] 



KNOWLEDGE 



195 



Its Plasmodium emerges from the wood in points about 

 the size of a pin's head, and is found to be differentiated 

 into two elements — (1) a transparent motile jelly, and (2) 

 an irregular network of opaque plasma embedded in the 

 transparent jelly. These two parts are shown in Fig. 16. 



Gradually little promi- 

 nences are developed on the 

 surface of the plasmodium, 

 and as these grow into the 

 finger-shaped projections, 

 the network of opaque 

 plasma appears just below 

 their surface, the trans- 

 lucent jelly of the interior 

 passing through the 

 strands of the network and 

 forming a very thin ex- 

 ternal coat. The next step 

 is taken when the strands 

 of this network thicken so 

 as to occupy nearly the 

 whole surface of the pro- 

 jection and then break up 

 into polygonal plates, each 

 furnished with a nucleus ; 

 from each of these plates 

 there grows a pedicel 

 supporting a ball which 

 is the future spore ; into 

 this the opaque plasma of 

 the plate passes. This 

 state of things is shown in 

 Fig. 17. When the spores 

 have fallen off, the rest 



Fia. 16. — Ceratomyxa mticida. 

 Plasmodium showing superficial 

 transparent jelly, and opaque 

 strands. (After Famiiitzin and 

 Woronin.) . 





Fl 



& 



^*^^ 



0'^ 



^;4.:^- 



i^ 



FlQ. 17. — Ceraiomfixa mucida. 

 Development of Spores x 160. 

 (After Famintzin and Worouin.) 



the plant withers and disappears, 



Each swarm spore, according to these authors, often 



shows amceboid move- 

 ments ; divides into two 'f*'; 



equal parts, which assume 



a cross-like posture in 



their greatest length, the 



one lying on the other ; 



then each of the two parts 



divides into two other 



parts and again each of 



the four divides into two 



parts, so that the original 



swarm spore is now 



represented by eight proto- 

 plasts all lying together ; 



these then separate, develop cilia, and act as free swarm 



spores. Fig. 18 represents the eight protoplasts lying cross- 

 wise together, before their final 

 ' i^^' ' separation. We are bound to add 



that this peculiar process has not 

 been noticed by Mr. and Miss 

 Lister in their numerous observa- 

 tions on Ceratomyxa, nor by our- 

 selves in our more limited ones, 

 and the matter appears therefore 

 to require further enquiry. 



AcBAsiE-E. —We have already 

 indicated the existence of a small 

 group of organisms differing from 

 the ordinary myxies in the fact 



that the swarm-spores, though they gather together and 



act together, never fuse into a single mass or constitute a 



true Plasmodium. 

 Three species have been studied and described with 



•s 



Fig. 18. — Ceratoiiii/.va 

 mucida. Eight Protoplasts 

 before their final separation. 

 (After Famintzin and 

 Woronin.) 



some care, and their history is so curious that we hope 

 our readers will not weary if we dwell upon it a little. 



The swarm spores are like 

 those of true myxies, and have ~ x 



the same amceboid movements, 

 but without the dancing move- 

 ment with flagellas. These 

 swarm-spores meet and, as if by 

 common consent, set up a centre 

 of attraction, towards which 

 they tend, the long arms or 

 straggling parts of the original , o 



gathering coming more and more 

 to the central point. , 



The course of growth in 

 Acrasis yranulata (one of the 

 organisms in question) has been ' 



described by Van Tieghem. ./ 



When the swarm cells have '' 



gathered together, they touch | ,.«:'i'; j 



one another, and form a cellular ' ■^■■' 



mass. This mass grows upwards •'.,■ 



in a conical shape. The cells of . .• ; 



the axis, somewhat longer than ^! 



they are broad, assume a cellular 

 membrane, and constitute a foot, 

 buttressed up by other cells. 

 The exterior cells move upwards 

 on this foot, clothe themselves . i 



with a cellular membrane, heap u 



themselves together at the :< 



summit of the structure, and , J 



thus form a chaplet of spores. 



In Dictyostelium mworouies a ^^^ \9.-Dict,osieHum 



very Similar course of growth has mucoroidei. Section, a, 

 been observed. The mass which Crown of Spores ; b, Stalk ; 



collects at the central point ''. Remains of Membrane 



differentiates itself into a ^™'^'^"^ .''•^ g''7''i "^ ^^^ 



, , ... Sporangium. (After cre- 



column, a membraneous veil to f Jj \ 

 the column, and a residual mass 



surrounding the column. As the column grows upward 

 this residual mass does the same, and thus withdrawing 

 its lower part from the ground it wanders up the stalk 

 and forms a cap or crown which turns into spores without 

 a trace of capillitium. Fig. 19 shows in section the 

 nearly adult form of this organism. 



A still more singular history is presented by a third 

 species, the PolysphondyUum ciolaceum. Here the early 

 stages correspond with those already described, the Plas- 

 modium, or more accurately the pseudo -plasmodium, 

 gathers itself towards a central mass as shown in Fig. 20 ; 

 the central mass again differentiates itself into a column 

 and a surrounding mass of protoplasm which clings round 

 the attenuated central column, as shown in Fig. 21 ; it 

 then begins to narrow in at intervals along this column, 

 and breaks up into discontinuous lengths with intervening 

 nodes, as shown in Fig. 22 {a). From these discontinuous 

 pieces of protoplasm there are subsequently developed in 

 the top of the column a terminal head, and on the successive 

 lower stages of the column, successive whorls of stalks, each 

 carrying a lateral and smaller head, as shown in Fig. 22 (6) ; 

 each of these heads finally ripens and breaks up into spores. 



The life-history of all these Acrasiea presents many very 

 curious points ; it seems to bring before us the fact that 

 separate protoplasts, without ever uniting into a plasmodium 

 or ever becoming part of a single organism, may never- 

 theless acquire as it were the social instinct and live for 

 the good not of themselves but of the whole organism, 

 and for that purpose may submit to a division of labour ; 



