PROGRESS OF MICROSCOPICAL SCIENCE. 
25 
I recommend the authors of our English Physiologies to overlook the 
stereotyped engravings in their several works on the subject. Not 
one, with the exception of Waters, gives a faithful delineation. I 
shall not trouble you with a description of how dry lung is affected 
with acetic acid of the above strength. Suffice it to say that turpen- 
tine, glycerine, Canada balsam, dammar varnish, and other materials, 
all fail to bring out the epithelium of the alveoli." 
Beproduction of Desmids. — Prof. Leidy, at a late meeting of the 
Academy of Natural Sciences of Philadelphia, made some remarks on 
the mode of reproduction and growth of the Desmids, which are 
reported as follows by the 'American Naturalist,' Nov., 1874. In 
illustration he described a common species of Docidium or Pleu- 
rotaenium. This consists of a long cylindroid cell constricted at the 
middle and slightly expanded each side of the constriction. When 
the plant is about to duplicate itself the cell-wall divides transversely 
at the constriction. From the open end of each half-cell there pro- 
trudes a colourless mass of protoplasm defined by the primordial 
utricle. The protrusions of the half-cells adhere together and continue 
to grow. The bands of endochrome now extend into the protrusions 
and subsequently keep pace with their growth. The protrusions con- 
tinue to grow until they acquire the length and form of the half-cells 
from which they started. The exterior of the new half-cells thus 
produced hardens or becomes a cell-wall like that of the parent half- 
cells. In this condition two individuals of Docidium are frequently 
observed before separation. During the growth of the new half-cells 
the circulation of granules in the colourless protoplasm is quite 
active. In a species of Docidium 1 J mm. long by -f^ mm. broad, the 
growth of the new half-cells was observed to be at the rate of about 
J mm. in an hour. 
The largest Apyrencematous Blood-corpuscles. — In a paper read at a 
late meeting of the Zoological Society, Professor Gulliver stated that 
in the Apyrensemata or Mammalia the largest red corpuscles of the 
blood are those of the two elephants, the Aardvark, two-toed sloth, 
and the walrus ; and that it is remarkable that the largest apyren^e- 
matous corpuscles should occur in three such different orders as 
Pachydermata, Edentata, and FeroB. In Pachydermata, excepting 
the elephants, the corpuscles are. by no means so large, not even in 
the hippopotamus, the corpuscles of which he had then measured for 
the first time. But the order Edentata is characterized by the large- 
ness of the corpuscles ; while among the FersB there are very large 
and very small corpuscles, the large ones being quite characteristic 
of the Pinniped family, as was shown by his recent measurements of 
the red blood-corpuscles of Otaria and TricJiecus. In the human sub- 
ject the corpuscles are exceeded in size by those of only eight or nine 
exotic Mammalia, and not equalled in size by the corpuscles of any 
British animal of the class. And this fact, independently of its phy- 
siological interest, may prove important in medico-legal inquiries ; 
since by it alone Dr. Joseph G. Kichardson states, in the September 
number of this Journal, that he has correctly distinguished dried 
stains of human blood from those of the ox and sheep. 
