ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 837 



division in various directions, and considers this phenomenon as the 

 commencement of a palraella-condition. 



A third and new species, described as C. pachyderma, showed a 

 special peculiarity of the vegetative cells. Asa rule the author found 

 imbedded in the transverse walls on each side of the cells, one, and 

 sometimes two, crescent-like particles of cellulose sharply pointed on 

 both sides, which were distinguished from the transverse walls by their 

 more highly refringent power. When the cells are about to trans- 

 form themselves into resting-spores, they increase somewhat in size, 

 the chlorophyll augments and distributes itself uniformly, but no new 

 membrane appears. It seems as if one, or, perhaps more strictly 

 speaking, two new pointed box-like interlocked layers are formed in 

 the inner, less watery, layer of the mother-cell-wall. The wall of 

 the resting-spore is therefore the thickened wall of the mother-cell. 

 The resting-sjiores escape through the conversion into mucilage of 

 the outer part of the cell-wall. In germination a hood-shaped piece 

 of the outer membrane of the resting-spore remains, which is 

 attached to the basal cell. 



In Conferva bombycina Ag. var. minor, either single cells swell up 

 into a barrel-shape, or here and there the contiguous ends of two neigh- 

 bouring cells assume a club-like form. It is here that the largest part 

 of the chlorophyllaceous protoplasm accumulates, and after this the 

 swollen end is separated by a transverse wall from the longer narrow 

 part of the mother-cell. The wall of the swollen part thickens later. 

 The author considers these cells to be resting-spores, although he was 

 not able to observe their germination. C. bombycina Ag. var. genuina 

 has similar resting-spores. 



We find accordingly that three modes of formation of the resting- 

 spores of Confervaceas have been observed, viz. (1) by rejuvenescence, 

 and the formation of a new membrane round the contracting contents ; 

 (2) by the thickening of the membrane of the mother-cell ; (3) by 

 separation of a portion of the cell-substance to a swollen part of the 

 mother-cell, and the thickening of the membrane of this portion. 



Diatoms of the Baltic* — H. Juhlin-Dannfelt has critically ex- 

 amined the diatoms of the Baltic, describing over 300 species, 

 including a number of new species and varieties. He finds them to 

 belong entirely to brackish forms, except where fresh water has mixed 

 with the salt, where many true fresh-water species occur. Comparing 

 them with the forms found in the quaternary diatom-beds of Sweden, 

 he finds no identical species, from which he infers a diminution in the 

 amount of salt in the Baltic in historic times. 



Motion of Diatoms.— Colonel B. O'Hara writes : " As the subject 

 of the movement of diatoms has been recently brought forward again, 

 the following notes on the subject may be of interest : — 



In washing away the acid from diatomaceous material, I have 



* Bihang til R. Svenska Vet. Akad. Haudlingar, vi. (1882) 52 pp. (4 pis.). 

 See Bot. Centralbl., xi. (1882) p. 153. 



