106 Dr. E. Greef on the Structure and 



But notwitlistancling all the labour that has been bestowed 

 both upon the bell-animalcules and upon the Infusoria in 

 general, notwithstanding numerous interesting individual ob- 

 servations, and especially notwithstanding the great abundance 

 of systematic materials, it appears that we are still far from 

 'having even a moderately satisfactory insight into the orga- 

 nization and vital history of the Infusoria — nay, that in many 

 respects we have perhaps made only the first still uncertain 

 steps in the knowledge of this remarkably multifarious class 

 of animals, in whose varied company we have to seek many 

 forms more or less allied to or constituting the parent forms 

 of other groups of animals, especially the Vermes and perhaps 

 the Coelenterata, and which, by their universal distribution 

 and their constantly recurring forms (in other words, by their 

 truly cosmopolitan character), possess a special interest pre- 

 cisely in the above-indicated direction of their relationships to 

 other animals. 



The material for the present observations was furnished, as 

 regards the freshwater forms, by the rich Infusorial fauna of 

 the Schlossweiher of Poppelsdorf and some other stagnant 

 waters in the environs of Bonn. Although I have submitted 

 many of the genera and species occurring here to careful in- 

 vestigation, in these communications some forms to which I 

 am indebted for the most abundant and important results are 

 brought prominently forward, especially a species of EpistyJis, 

 which nearly approaches Ehrenberg's Ejnstylis favicans. I 

 say " nearly approaches," as I greatly doubt whether all the 

 forms here noticed by me under this name belong to a single 

 species, or, rather, whether we have not before us several dif- 

 ferent species or, at least, varieties, as, indeed, a glance at the 

 appended figures (Pis. XV. & XVI.) may show. Not only 

 do differences of size, colouring, and even, although in a less 

 degree, of habitus occur, but also in the possession of appa- 

 rently essential parts (that is to say, of organs) , e. g. the pe- 

 culiar shining capsules, hereafter to be described, which are 

 furnished with a filament capable of being shot forth, and 

 which display a close agreement with the nettling-capsules of 

 the Coelenterata (PI. XV. fig. 5,k). In the course of our 

 communications we shall again revert to the distinctness or 

 identity of these forms. 



The marine species which I have had the opportunity of ex- 

 amining are all from the North Sea at Ostend, where the oc- 

 currence of abundant material was always certain, especially 

 in the oyster-parks there. These marine forms are represented 

 on Plates XII. & XIII. (with the exception of fig. 8 on 

 PI. XIII.), in which the act of division and the gemmiform 



