478 Prof. Stein on the Development and 



iwi^.'^' The cysts may, as the experiment cited above show?, 

 remain diy a long time, and yet their development will proceed 

 as soon as they enter water again. 



In the same way the wind may readily carry away Vorticella- 

 systems with the dust from dried-up pools. Should any one think 

 these suppositions too bold, let him examine the dry sand of the 

 roof-gutters, as two years ago I did frequently in order to make 

 my pupils acquainted with the Tardigrada. Not uncommonly, 

 besides Tardigrada and their ova and different Rotifera, we find 

 Vorticella-cysts which may be readily recognized if the inclosed 

 body is yet unchanged. These cysts were either deposited in the 

 gutters by the winds, or they are the descendants of Vorticella, 

 which came in this way and multiplied in the rain-water collected 

 in the gutters. 



I may be allowed, in conclusion, to recur to the starting-point 

 of my investigations upon the Infusoria; this was, my researches 

 upon the Gregarimie. The hope of finding the Infusoria not 

 much more perfectly organized than the Gregarince, and of dis- 

 covering a similar law of development for them, encouraged me 

 to enter upon the investigation of that difficult and famous class. 

 This hope has been fulfilled. Without at present entering into 

 any controversy upon the organization of the Infusoria, con- 

 cerning which, after the course of development we have traced, 

 there will perhaps be no doubt, 1 will only point out how the 

 law of development enunciated by me for the GregarincEj essen- 

 tially harmonizes with that which governs the Vorticellce, 

 iHlffhe Gregarince become encysted for the purpose of propa- 

 gation like the VorticellcSj only it is always two Gregarina which 

 become included in one capsule. The two encysted Gregarince 

 fuse into one ball, and then a great part of the contents of their 

 bodies becomes changed into spindle-shaped spores (the so-called 

 7iaviceUce), whilst the remaining portion liquefies in order 

 to contribute to the bursting of the cyst and the expulsion of the 

 ripe spores. The encysted Vorticella changes also into a simple 

 globular body, and then its germ-nucleus breaks up into nume- 

 rous round discs. There is no reason why these should not be 

 called spores. These spores however become developed into em- 

 bryos in the parental cyst. Finally, the cysts burst, and, like the 

 spores of the Gregarinidse, they are driven forth swimming 

 in a part of the liquefied contents of the body of the parent. 



The investigations upon the Vorticellce may be considered to 

 strengthen those upon the Gregarinidse. I bring forward the 

 Gregarince into prominence here intentionally, because I see 

 that lately two very estimable observers, Bruch* and I^eydigf, 



* Siebold und KoUiker's Zeitschrift, B. ii. 



t Miiller's Archiv, 1 85 1 . 'J 



