STAK-LIKE ANIMALS. 119 



immobile parental form the young are, on the con- 

 trary, very active ; they jump and dart about with 

 great rapidity, are fringed with cilia, and may easily 

 be mistaken for other minute ciliated infusorians. 

 There is reason to think that such has been the 

 case. However this may be, let us now try and 

 watch the active ciliated body before us. This is no 

 easy task ; at last, however, one stops its gyrations 

 and rests on a bit of algse. It is undergoing a 

 change ; the cilia disappear, and a slight projection 

 is observed at the point of greatest density, where 

 a pedicle is gradually developed. This gets fixed to 

 the weed. Now the body begins to enlarge, and 

 gradually little by little the well-known corners 

 appear, and the shining tufts of tentacles are pro- 

 duced ; and, finally, you have a mature Acineton 

 under your gaze. All this transformation is some- 

 times effected in about an hour or so. It is not 

 always, however, that the process is of this rapid 

 and continuous order. Sometimes the little ciliated 

 embryo takes a turn at multiplication on its own 

 account, and, instead of at once developing into a 

 full-blown Acineton, chooses to perform the com- 

 mon process of fission, or self-division, before pass- 



