FRESIIWATKR IHIIZOPODA. 2§3 



ment of a great basket-work of the same structure constitut- 

 ing a hollow globe, such as would have filled an entire plate 

 if drawn to the scale adopted. 



Omission of Leptothrix forms by Professor Cohn. — Very 

 abundant in many growths of Bacterium rubescens are long 

 Leptothrix filaments containing loculi coloured by Bacterio- 

 purpurin. Of these and their significance Professor Cohn 

 omits all mention. The fact that they exist and that between 

 them and the biscuit-shaped or oblong plastids tliere are com- 

 pletely transitional forms, such as those figured in pi. iii, fig. 3, 

 of this Journal, January 1876, is sufficient to upset once 

 and for all the position taken up by Professor Cohn, to the 

 effect that the Bacteriacese can be arranged in two natural 

 series the one containing Micrococcus and Bacterium parallel 

 to the Chroococcacese — the other containing Bacillus, Vibrio 

 and Spirillum parallel to the Oscillarife. According to Cohn 

 the first series have their quiescent stage exclusively as gloe- 

 ogenous cell-families; whilst the other series have their 

 quiescent stage exclusively as Leptothrix filaments. 



The fact that Bacterium rubescens occurs both in the 

 glceogenous (chroococcaceous) and the leptotrical (oscil- 

 larian) conditions renders this classification of Cohn's quite 

 erroneous. 



Moreover it is to be remarked that the active movement 

 of leptothrix-forms and of Oscillarise renders a balancing 

 of them against the vegetative resting stage of Chroococcacese 

 inappropriate. 



Resume of Recent Contributions to our Knowledge 

 of "Freshwater Rhizopoda." Part I. Heliozoa. 

 Compiled by Wm. Archer. (With Plate XXL) 



A LARGE number of contributions to our knowledge of 

 " Freshwater Rhizopoda " have recently made their appear- 

 ance in Germany in the ' Archiv fUr Mikroskopische 

 Anatomic,' formerly edited by Max Schultze, and as it is not 

 unlikely that a careful and diligent out-look may reward 

 observers in our own country with the discovery from time 

 to time of some of. the interesting new forms brought to light 

 in these Memoirs, it has been thought that a resume contain- 

 ing as complete an account as our space permits Avill be of 

 interest to the readers of this JournaL 



