420 Mr. H. J. Carter on the Development of Sorastrum, 



LI. — A Descrtjytion, with Illustrations, of the Development of 

 Sorastrum spinulosum, Ndj. ; to which is added that of a new 

 Form o/" Protococcus. By Henry J. Carter, F.E-.S. &c. 



[Plate XIV.] 



Introductory Remarks. 



On the 29th of January of the present year (1869), I collected 

 a little of the surface-mud and water of a pool in a heath-bog 

 about a mile from this place (Budleigh-Salterton), and, having 

 poured it into one of those three-and-half-ounce greenish glass 

 gum-bottles, of a pyramidal shape (that is, flat and expanded 

 at the bottom, with a narrow mouth), in which a solution of 

 gum is now generally sold in the shops for adhesive purposes, 

 I submitted some of it to immediate examination ; and finding 

 that it contained many sporangia, together with large Pinnu- 

 lariw, I resolved to keep it throughout the spring, to see what 

 changes might take place in either ; for, from the presence also 

 of many Desmids, especially Closterium, I thought that some 

 of the sporangia might belong to the latter. 



The gum-bottle was kept on a table close to a window 

 facing due west ; and time after time portions of the sediment 

 were extracted with a dip-tube and placed under the micro- 

 scope for examination, while the water in the bottle was re- 

 plenished from a deep well, as required. 



It was not, however, until about the second week in Jime 

 that I began to find many of the sporangia developing fila- 

 ments of ^jjirogyra and Zygnema i-espectively, which, accumu- 

 lating, soon floated to the surface of the water in a dense mass. 

 The Pinnularice presented no change beyond an increase of 

 their glairy globular contents ; but a great many sporangia 

 remained, in some of which I still hoped to see the develop- 

 ment of some Desmid. 



On the 18th July this long-looked-for phenomenon seemed 

 to present itself, by the presence m a sporangium under ob- 

 servation of a triangular organism so very like the Desmid 

 Staurastrum dejectum (Ralfs, Desmid. pi. 20. fig. 5) that I made 

 sure of having found the zygospore of at least one kind of 

 Desmid under development. 



It was not likely, therefore, that I should tlirow away this 

 0]:»])()rtunity, and so I took the measurements of the sporangial 

 cell and of all its contents respectively ; but in doing this, it 

 became evident to me that the triangular Desmid was not the 

 one I had taken it for, but another, of a kind with which I was 

 unacquainted. 



This made ine still more particular ; and so I not only 



