INVERTEBBATA, CRYPTOGAMIA, MICROSCOPY, ETC. 139 



the same species true adventitious branches sometimes arise on old 

 parts of the thallus, which, however, do not materially afifect the 

 habit of the plant, and are always clearly distinguished, by their posi- 

 tion on the midrib of the thallus, from the normal endogenous 

 branches, which are always marginal in their origin. 



Revivification of Diatoms.* — Professor Hamilton L. Smith, 

 referring to the observations of Mr. F. Habirshaw and Captain Mor- 

 timer, t as to the revivification of some diatoms after six years, says that 

 while there can be no doubt that living diatoms were found as stated, 

 proof is yet needed that they were really reihified. It is contrary to 

 experience hitherto ; indeed, it is well known, and one of the means 

 employed to procure purer gatherings, that oftentimes apparently 

 pure water will, if allowed to stand quietly, show an abundant crop 

 of diatoms. In many cases that he has noted of the appearance of 

 living diatoms after wetting long-dried material, they have been, not 

 the forms originally in the gathering, but those evidently derived from 

 the water. At present, while we may, and perhaps must, admit that up 

 to a certain limit diatoms, like the rotifers, may be dried, with power 

 of revivification or reproduction, there is yet lacking sufiicient evidence 

 that their drying may extend over a series of years. 



Classification of Desmidieae.| — In his investigation of the 

 desmids of Eastern Prussia, Klebs has redescribed and reclassified 

 the species belonging to the important genera Closterium, Penium, 

 and Cosmarium. 



It may be stated that the general result of his researches has been 

 to render much less distinct than has heretofore been supposed the 

 boundary-lines of both species and genera. In a large number of 

 cases he shows how well-known species hitherto considered distinct 

 pass imperceptibly one into another. Even as regards the genera, 

 Penium is so closely allied to Closterium as hardly to admit of 

 satisfactory discrimination ; P. margaritaceum furnishing a direct 

 transition to the striped or banded closteria like C. intermedium. 

 Cosmarium Thwaitesii is again closely allied to Penium through 

 P. closterioides. Pleurotenium cosmarioides de By., tlic author con- 

 siders to be a form of Cosmarium de Baryi. A similar review of the 

 remaining genera of Desmidiea) will probably follow. 



Parthenogenesis in a Spirogyra.§ — In a quantity of a Spirogyra 

 (probably S. arcta Ktz.), from spring water with a rocky bottom, 

 H. Ziikal observed an abundant formation of spores (like zygospores) 

 without any previous conjugation. The spores were formed, in some 

 instances, in two, three, or even six adjoining cc-lls, without the least 

 trace of the formation of projection from the cells, or other prelude to 

 conjugation, and they resembled in every respect those formed in the 

 ordinary manner. They also escaped in the same manner from the 



* Bnird's ' Anmiul R( cord of Science and Industry ' for 1878 (1879) p. 370. 

 t This Journal, i. (1878) pp. l.JO and 311. 



X ' Uel)er die Fortnen eiuiger Gattungeu der l)(>sinidiacecn Ostpreussens,' 

 von G. Klol)3, Konigslwrg, 1879; see ' Iledwigia,' xviii. (1879) p. 150. 

 § 'Oc.-stcrr. Hot. Zcitschr..' xxix (187:0 p. 291. 



