430 PROF. A-LLMiLiS" ON THE BECENT RESEAECHES 



the cyst burst (C), and a multitude of the red pear-shaped bodies 

 issued from it and moved about in the surrounding water. It was 

 soon seen that one end had become attenuated into a very fine 

 tail or flagellum (D), so that the free sporules resembled the Pla- 

 gellatae, or the zoospores of an Alga. They were without a trace 

 of nucleus, or of contractile vesicle, or of investing membrane, and 

 consisted solely of minute naked masses of homogeneous proto- 

 plasm. 



This swarming-period lasted about one day, and then the spo- 

 rules lajf quiet on the bottom of th.e vessel. The tail was drawn 

 in, and the pear-shaped form was changed into that of an irregular 

 roundish disk, from whose circumference pseudopodial processes 

 began to be emitted. The sporule had now passed into the con- 

 dition of an Amoeba (E), and began, like an Amoeba, to take in 

 nutriment by engulfing it in its substance ; and then vacuoles of 

 inconstant size and position made their appearance within it. 



Two or more of these Amoebce were seen to unite and form a 

 Plasmodium. The pseudopodia became more and more branched 

 and reticulated, and the condition of the orange-red dendritic 

 patches, which crept over the Spirula-^\veVL, and with which our 

 liistory commenced, was finally attained. 



It is thus seen that Protomyxa passes in the course of its de- 

 velopment through an encysted or sedentary stage, and a free or 

 mobile stage. The latter shows itself in three different succes- 

 sive forms : — 1, that of a free-swimming flagellate; 2, that of a 

 creeping Amoeba ; and 8, that of a contractile protoplasm-net. 



The genus Myxastrum, represented by M. radians (fig. 15), was 

 also found by Haeckel in the Canary Islands. It consists of a small 

 globular mass of homogeneous protoplasm (Gr), from whose whole 

 periphery radiate a multitude of fine pseudopodia. It thus bears 

 a close resemblance to the well-known ActinopJirys sol, from which, 

 however, it is separated by the absence of vacuolse and by its 

 remarkable mode of reproduction. 



When the time for its reproduction approaches, Myxastrum 

 radians retracts its pseudopodia, assumes the form of a smooth 

 ball, encysts itself in the manner of Protomyxa, and becomes 

 motionless (A). After a time the plasma mass within the cyst be- 

 comes divided by radiating furrows into numerous segments, which 

 gradually assume a spindle-shape and become clothed with a thin 

 siliceous membrane (B, C). These spindle-shaped bodies resemble 

 Naviculce, and if isolated might easily be taken for small Diatoms. 



