1868.] 363 [Edwards. 



searching investigation. If the whole frond of a Homoeocladia with 

 its myriads of enclosed frustules is an individual, then is the usually 

 free Nitzschia, a single frustule of which can not be morphologically 

 distinguished from a single detached frustule of Homoeocladia, also an 

 individual'? and is a Navicula an individual as well as the group of 

 similar forms enclosed within the tube of a Scldzonema or the gelat- 

 inous frond of a il/«A7o^^o<«'? Again is a Ci/clotel/a an individual as 

 well as the long chain of discs which go to make up the fi-ond of a 

 Melosira or Podosira '? Upon this point I shall, hereafter, have more 

 to say, merely begging the record of an observed fact bearing thereon 

 by students of this extremely interesting, and, I am convinced, import- 

 ant branch of natural history. 



I desire to place on record that I have seen at least two, apparently 

 and generally acknowledged free species of Desmidiacete, attached to 

 a submerged aquatic moss. One was a Closterium, species not deter- 

 mined, which was for a long time (as during the most of last summer 

 the specimens were growing in one of my aquaria) attached pretty 

 firmly, by means of a true stipes or stalk of no great length, to the 

 leaves of the moss, and that so strongly that It required some' con- 

 siderable force to detach it. By rocking the covering glass 

 upon the slide, upon which the specimen of moss Avas placed 

 during observation by means of the microscope, the Closterium could 

 be made to swing about from side to side upon its stipes without 

 becoming detached. The other species, observed at the same time, 

 was a Micrasterias, and this was fixed, generally in pairs, to the same 

 moss, by its broadest side, or by both valves, so as to present a "fi'ont 

 view" (as it is termed when speaking of Diatomaceaj), to the observer, 

 thus presenting an analogy to the genus Epithemia of that family 

 which occurs growing after the same manner; Cocconeis, on the con- 

 trary, is attached by means of the whole of one of the valves. The 

 stipes of the Closteriu?n was, of course, at the end of the frustule 

 where the valve comes to a jDoint, after the manner of a Cocconema, 

 which genus Closterium resembles much in form. In neither of these 

 cases do I designate the species, as that I deem hardly of importance, 

 the mere fact of Desmidiaceaj being found under such conditions 

 being the important one. At the same time, it is as well to mention 

 that these species were thus found during the month of August, or in 

 the midst of the summer, the same forms having been observed fi.'ee 

 and moveable in the early part of the spring. 



I have now to place upon record, my opinion that the Desmldi- 

 acefe are governed by very much the same law as applies to their 

 apparently near allies the Diatomacese ; that is to say, that they are all 

 at some period of their existence attached, and at another free. 



