PROGRESS OF MICROSCOPICAL SCIENCE. 
35 
be seen progressing steadily inwards by the parting of tbis thin double 
membrane, so that in fifteen or twenty minutes tbe fissure is complete. 
He has, in very large Pinnularice, witnessed the whole phenomenon, 
from its inception up to the final self-division. While the fissure 
occurs in the short period of time named, to complete the self-division 
requires about six days. The part which slips out has, of course, one 
of the old valves upon it. Again, by self-division, the new valve 
becomes an old valve for the second-formed frustule ; and so the frus- 
tules become smaller and smaller, as stated by Braun, ‘ Rejuvenes- 
cence in Nature,’ Ray Soc., 1853, p. 132, The minute forms are, 
indeed, younger, or more newly formed, and, of course, more numerous. 
At this juncture, conjugation occurs, and a return to the normal con- 
dition of the original large frustule, by the formation of a sporangial 
frustule of double the size of the parent frustules. The following 
seems to be the author’s admission of the peculiar elevations which 
undoubtedly exist in a certain number if not all cases. “ As regards 
the terms “ costas ” and “ striae,” the distinction is altogether too 
vague to rely strongly upon them as characters ; the term pervious 
costate, or striate, is sufficiently decided. Mr. Slack’s researches 
appear to prove that even the coarsest costae are simply very close or 
confluent dots. Only in the small forms, however, will any difficulty 
be experienced in deciding between costate and striate, as these terms 
are generally understood ; probably here other characters will decide, 
leaving in these obscure cases the kind of marking as undecided.” 
Connection between Pycemia and Bacteria. — At a recent meeting of 
the Pathological Society (May, 1872), Dr. Sanderson gave a series 
of demonstrations the object of which was, we believe, first to show 
the presence of bacteria in the infecting fluid of pyfemia, in the blood 
of living pytemic patients, and in pysemic abscesses ; and, secondly, to 
prove that these living organisms were not introduced into the body 
from without, but were apparently produced within the body. It will 
be remembered that in certain experiments recorded in one of the 
reports of the Medical Officer of the Privy Council, Dr. Sanderson had 
shown that bacteria were introduced into fluids by contact with im- 
pure surfaces, and that when glass-rods, test-tubes, and the like, had 
been heated before being brought into contact with fluids, no bacteria 
were therein developed. Dr. Sanderson, we believe, had taken care in 
his experiments on pyaemia to avoid the introduction of germs from 
without into the peritoneal cavity. He first showed the liquid taken 
from the peritoneum of a guinea-pig twelve hours after the injection 
of fluid into it from the peritoneum of a kitten in which peritonitis 
was excited by the injection of peritoneal fluid. This liquid was 
swarming with minute bacteria, chiefly spheroidal, this beiug the 
feature of the liquids possessing the most intense infective character. 
The second specimen was the blood of an animal infected as the 
guinea-gig, and bacteria existed in the blood of the living animal 
taken from the heart. The existence of these organisms in the blood 
was regarded as the index of the general state of infection. The third 
fluid was that contained in the peritoneum of a guinea-pig twelve 
hours after injection into that part, of the subcutaneous fluid formed 
