474 Prof. Stein on the Development and 



sometimes suddenly disappeared to reappear elsewhere. I be- 

 lieved now that this was the commencement of the metamor- 

 phosis of the Vorticella-cysts into the Acin eta-form. 



But, seeking further, I came upon cysts in which one or a few 

 of the csecum-Uke projections of the parental vesicle had become 

 so much elongated that they had broken through the covering 

 of the cyst. Looking steadfastly at such a projection, it sud- 

 denly burst at its apex and the whole contents of the parental 

 vesicle shot out, whilst its walls collapsed, and remained behind 

 like an empty wrinkled bladder with a few adherent granules, 

 within the cyst. 



The free contents remained as a round, transparent, limpid 

 drop of jelly of about the same diameter as the cyst, in: which 

 some thirty embryos, of the form of Manas colpoda or Monas 

 scintillans, sailed about with varied and active motion as if in a 

 lit'lle ocean. 



After a time the drop of jelly became diffused, and its monadic 

 inhabitants were scattered to the winds. More clearly and de- 

 cidedly could no observation be made than that just described ; 

 yet I should have been ready to believe myself deceived by some 

 singular accident, had I not, in the following hours which I 

 passed with beating heart at my microscope, seen the very same 

 process in many cysts as distinctly and decidedly as the most 

 scrupulous criticism could require. Soon also I succeeded in 

 bursting cysts, ripe but perfectly closed, by careful pressure, so 

 as to see theiembryos slip one after another out of the parental 

 vesicle., in ashmsi^iLi u\m[ 



I now proceeded to examine the mode of origin of the em- 

 bryos more closely, in which I succeeded all the better, as I pos- 

 sessed cysts of very different ages ; for in a few I found the yet 

 unchanged Vorticella-body. 1 observed that in cysts, whose in- 

 cluded Vorticella-body w^as metamorphosed into a simple vesicle, 

 the band-like nucleus had broken up into as many single disci- 

 form bodies as, later, embryos were to be set free. This break- 

 ing up does not take place by successive acts of division, but in 

 the nucleus, round discs become marked off contemporaneously, 

 at the most different points ; whilst the intermediate substance 

 of the nucleus becomes reabsorbed. The discs grow at the ex- 

 pense of one part of the liquefying granule-substance of the 

 parental vesicle, whilst the other part becomes changed into the 

 gelatinous mass, in which, afterwards, the embryos swim. The 

 perfect embryos are oval, somewhat notched on one side, and 

 wholly similar to the Monas colpoda, Ehr., or the M. scintillans, 

 but quite dissimilar to a Vorticella, The walls of its body are as 

 flexible as those of all ciliated Infusoria ; but beside this general 

 contractihty, they unquestionably possess special motor organs ; 



