210 PROGRESS OF MICROSCOPICAL SCIENCE. 
between the dead thin-walled cells of the fundamental tissue, cells 
which not only retained their protoplasm and chlorophyll, but had 
increased the volume of the latter in particular in a striking degree. 
These occurred in the decayed tissue, sometimes isolated and some- 
times in groups, the individual cells arranged beside or above each 
other. Even from cells in the wall of the capsule Dr. Stahl found 
protonema filaments to proceed. From Pringsheim’s observations, as 
well as from those here communicated, the conclusion is clearly 
arrived at that the transition from the spore-bearing generation to 
the sexual generation is not necessarily bound up with the formation 
of spores, but that, under conditions injurious to the formation of 
spores, different cells, both of the seta and the capsule, are capable 
of producing a protonema. 
The Origin of Pycnidia.—A difficult research is that which has 
been made by Dr. H. Bauke, and which is recorded in the ‘ Nova 
Acta’ (Band 36), Dresden, 1876. The original paper is abstracted at 
considerable length in the ‘ Journal of Botany’ (January), from which 
the following conclusions may be taken as stated by the author :—“ As 
to the question whether the Pycnidia are independent organisms, or 
whether they belong to the Ascomycetes, these researches prove the 
second of these alternatives to be correct. The cultivation of the 
Ascospores of Pleospora polytricha, Cucurbitaria elongata, and Lepto- 
spheeria (Pleospora) Doliolum regularly yielded Pycnidia—in the first 
of the three species named such bodies were up till now unknown; in 
this case the direct connection between the sown Ascospores and the 
Pycnidia was each time established. From Pleospora herbarwm, in 
spite of numerous cultivations instituted for the purpose of studying 
specially the development of the Perithecia and the Pleomorphism of 
this fungus, I obtained only twice Pyenidia. . . . In the cultivation 
of Melanomma (Spheria) Pulvis-Pyrius and of Pleospora pellita a dense 
mycelium was regularly produced, on which in the latter species the 
Conidia drawn by Tulasne appeared in masses, but no Pyenidia, which 
were indeed never found on either, &c. From Cucurbitaria Laburni 
and Pleospora Clematidis the same results were obtained, namely, no 
Pyenidia. Pycnidia appear as parasites on other Ascomycetes (as in 
the case of Cincinnobolus and Erysiphe) only as distinct exceptions.” 
Tubular Degeneration of the Medullary Nerve Sheath. — The 
‘American Journal of Insanity’ (January 1877) says that in partial 
softening of the spinal cord, and in grey degeneration, Professor 
Arndt observed—by examining transverse sections, coloured with car- 
mine—the medullary sheath to consist of concentric layers. As the 
medullary substance showed an inflated condition, there was no doubt 
of a pathological alteration; but still, Arndt believes that it also 
establishes the true structure of the sheath, which normally, very 
probably, grows by forming concentric layers. 
Are Volvox globator and Sphcerosira volvox distinct Species ?—This 
question has at length been answered in the negative by Mr. W. H. 
Gilburt, who has a short but important paper on this question in the 
‘Journal of the Quekett Club’ (February 1877). The relationship 
