346 Dr. F. Cohn on a new genus of the family 0/ Volvocinese. 



Gonium, Pandorina and Volvox agrees in all essential particulars 

 with the laws of propagation^ which I have just described in 

 Stq)hanospha>ra, as will be shown elsewhere. We may call the 

 mode of multiplication of the VolvociiiecB by the general name 

 oi propagation by macrogonidia. 



Another process is met with in Stephanosphara, besides the 

 above, and which I have observed more rarely, viz. propagation 

 by microgonidia. In this mode of multiplication the introductory 

 processes are exactly like those of the formation of macrogonidia ; 

 in particular each primordial-cell is at first divided into two, then 

 into four, and lastly into eight secondary-cells. But instead of 

 this third generation being permanent and becoming free, as is 

 usual, it not unfrequently happens that the process of division is 

 not arrested with the separation into eight; that the original 

 primordial-cell becomes parted off a fourth, fifth, and even a sixth 

 time, in the same manner, and at length is broken up into a large 

 number of cells (16, 32, 64), which naturally are so much the 

 smaller the greater number of times the subdivision into two 

 has taken place (fig. 16). While, moreover, in the formation of 

 macrogonidia, the secondary cells become surrounded by a com- 

 mon envelope, and are not free as an entire, connected family of 

 cells, arranged according to a definite law, in the mode of pro- 

 pagation now described the little secondary cells finally become 

 totally separated from one another, without secreting an envelope- 

 cell, and in this way each of the eight original primordial-cells is 

 broken up into 32-64 independent, green, elliptical or spindle- 

 shaped corpuscles, which then separate from one another, com- 

 mence an independent and active motion, and fill up, in great 

 numbers (as many as 256-512), the common parent-envelope- 

 cell. These little cellules — I shall follow the example of Alex. 

 Braun and call them mici^ogonidia — exhibit a very active and 

 energetic motion inside the envelope-cell, hurrying very rapidly 

 up and down in all directions in its cavity; producing by their 

 great number that curious swarming which Alex. Braun has very 

 aptly compared with the intermingling of a crowd of people in a 

 confined area, where every one is constantly changing his place, 

 while the whole together constantly occupy the same space. 

 This crowding in among each other of the microgonidia of Stepha- 

 nosphcera presents a picture fixing the attention in the highest 

 degree; sometimes the cellules arc scattered in a few large 

 masses ; then they unite again into a knot in the middle ; every 

 moment the general aspect varies (figs. 17 & 18). At length 

 the common envelope is ruptured here also ; then the microgo- 

 nidia emerge one after another or in large masses, but free and 

 singly, into the water (fig. 1 9 «) . Their true form may be then 

 readily detected by killing them with iodine ; they are spindle- 



