ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 787 



from tlie ends and gradually drawing together towards the more central 

 parts. This is the case chiefly with the two-celled rodlets. In the 

 longer ones the corpuscles make their appearance about the middle of 

 the rodlet. When these forms have attained a certain size and distinct- 

 ness, the plasma surrounding them gradually clears tip and they seem as 

 if environed by a bright halo. The brightness of the spore afterwards 

 disappears and it assumes the pale homogeneous appearance of the 

 vegetative rod, and, though still roundish, attains the ordinary breadth 

 of the rods. In this transition from the spherical to the cylindrical 

 shape no striation of the spore membrane is observable. The membrane, 

 like the parent-cell, seems to disappear by dissolution or absorption. 

 The spores, however, remain inclosed in a general gelatinous invest- 

 ment, which may contain from two to eight rodlets. The arrangement 

 of these rodlets in relation to the common envelope and to each other is 

 quite irregular. 



The author then proceeds to notice the effect of iron or its rust on 

 £. muralis. The accidental mixture of some scales of rust produced 

 a dark olive-green colour in the zooglcea mass surrounding the rust. 

 Examination under the Microscope showed that each cell-membrane was 

 now distinctly laminated or consisted of a number of concentric layers. 



Two mosses were found thriving luxuriantly on the zooglcea, Ephe- 

 merum tenerum and EpJiemerella recurvifolia. 



Prof A. Hansgirg * replies at some length to Prof. Tomaschek, 

 and at the same time takes the opportunity of copiously recapitulating 

 certain facts bearing on the subject of jelly -formation by Algse. 



Tomaschek had pointed out that B. muralis differs from AjpTianothece 

 caldariorum Eichter in being green. This, says the author, is of no 

 consequence, inasmuch as Algee grown without access of light become 

 blanched. He considers that not only is the green rod of B. muralis 

 identical with its colourless variation known as Plectonema gracillimum 

 (Glaucothrix gracillima Zopf), but that there exists a coccus form derived 

 by continuous subdivision which is common to Plectonema gracillimum 

 and B. muralis. 



The author points out that Tomaschek himself throws some doubt on 

 the truly bacillous nature of B. muralis, as he was unable from direct 

 observation to trace the transition from the motionless rod to the mobile 

 condition, a stage which is easily ascertainable in the transformations of 

 real bacilli. 



The author then turns to the highly refracting granules found at the 

 ends of the rods both in Aphanoihece caldariorum and B. muralis. In 

 the latter Tomaschek considers that they are intimately connected with 

 endogenous spore-formation, while Prof. Hansgirg says that there is no 

 difference between the corpuscles, and is disposed to regard them simply 

 in the light of the resting cells (aplanospores, cysts) of Algse and Fungi. 



Eeferring to the gelatinous laminated sheath, Prof. Hansgirg shows 

 that the formation of jelly is not uncommon in certain kinds of Algse, 

 and that this sheath may consist of several layers, the innermost being 

 the most recent. 



Spore-formation in Bacteria.f — Dr. A. Prazmowski deduces from 

 his experiments on micrococcus and bacterium that the earlier view 



* Bot. Centralbl., xxxv. (1888) pp. 54-7, 102-9 (2 figs.), 

 t Biol. Centralbl., viii. (1888) pp. 301-7. 



