450 THE MICROSCOPE. 



the conversion of an encysted Vorticellina into an Acineta. 

 He also considers Actinophrys Sol and Podophrya Jixa 

 (Ehr.) to be the acinetiform representatives of Vorticella 

 microstoma. 



Stentors, Trichodina, and a few others are included by 

 some authors in the Vorticellina. Stentors (fig. 22G, No. 4) 

 are exclusively found in fresh water, between or upon 

 water plants in still running waters. Some are colourless, 

 otbers green, black, or clear blue. " It is," says M. Du- 

 jardin, " in the Stentors where we can view the several 

 supposed internal organs isolately, and that new observa- 

 tions will make known their real nature." 



Rotiferoe comprise animals which were placed by 

 Ehrenberg in nine genera ; named Ptygura, jEcistes, Cono- 

 chilus, Megalotiocha, Lacinularia, Tubicolaria, Limnias, 

 Melicerta, and Cephalosiphon. As, however, each of these 

 genera contain but a single species, Mr. Gosse proposes to 

 reduce the nine to two ; thus, Ptygura, jEcistes, Tubico- 

 laria, Limnias, Melicerta, and Cephalosiphon, as they seem 

 to be only so many species of one genus, might constitute 

 one, and Megalotrocha, Lacinularia, and Conochilus, an- 

 other. Mr. Gosse also wishes to construct a family to be 

 called Melicertodos; in this he would include two genera, 

 Melicerta and Megalotrocha, degrading some of the present 

 genera to form species of Melicerta, and others, to constitute 

 three species cf Megalotrocha. Each group will be readily 

 distinguished — the former by the circumstance that the 

 individuals are solitary ; in the latter they are, in adult 

 life, aggregated in a common envelope — spherical masses, 

 composed of many animals radiating from a central point. 

 These compound masses are either free or fixed. In the 

 genus Melicerta, or tube-dwellers proper, the front 01 

 upper part of the body is capable of being turned in 

 upon itself, concealed with purse-like folds, and of being 

 expanded, at the will of the animal, into a disc form, which 

 is usually much wider than the diameter of the body ; 

 this again is either flat or in the form of a shallow funnel. 

 Its outline will form either a simple circle, as in 31. pty- 

 gura and M. cecistes, two circles united at one point, as in 

 Limnias (Plate III. No. 72), or four sinuous lobes, more or 

 less developed, as in M. cephalosiphon, M, tvhicolaria, and 



