PROGRESS OE MICROSCOPICAL SCIENCE. 
221 
divisions, and transformed themselves into large tubes composed of 
three superimposed barrel-shaped cells. The basilar cells, which 
were the longest and narrowest, soon pushed out curved lateral 
branches, and were followed by the median cells. The branches, 
which were multicellular and ramose, pressed against each other ancl 
formed a little white tubercle, the beginning of the fruit. 
The “ Membrana Nuclei ” in the Seeds of Cycads. — At the meeting 
of the Linuean Society, on March 4, Professor Tliiselton Dyer read 
a brief note on the structure of the so-called “ membrana nuclei ” in 
the seeds of Cycads. Heinzel had described this as a cellular struc- 
ture, the cells of which had thick walls penetrated by ramifying 
tubes. There is reason, however, for believing that the membrane 
only represents the wall of a single cell, and is, in fact, probably the 
greatly enlarged primary embryo-sac. What Heinzel had taken for 
tubes seemed really to be solid. They are arranged all over the 
membrane after the fashion of what carpet manufacturers call “ moss- 
pattern.” They are possibly the debris of the thickened walls of the 
cells of the nucleus which had been destroyed by the enlargement of 
the primary embryo-sac. In the discussion which ensued a remark- 
able diversity of opinion was displayed among the microscopists 
present, as to whether the reagent magenta exhibits the largest amount 
of its characteristic reaction on the cellulose wall of the cell, or on 
its protoplasmic cell-contents. 
Where do the White Corpuscles get through the Blood-vessels f — 
This question is answered by M. L. Purves in a recent number of a 
Utrecht Journal, which has been abstracted in the ‘ Medical Record ’ 
lately by Dr. W. Stirling. It states that M. Purves, in order to in- 
vestigate the place where the white blood-corpuscles pass through 
the wall of the vessel in Cohnheim’s experiment on inflammation, 
injected a solution of silver into the vessels of a frog prepared after 
the manner of Cohnheim. The colourless corpuscles, without ex- 
ception, wander out between the boundaries of the epithelioid cells. 
They never pass through the substance or through the nucleus of an 
epithelioid cell. According to the author, the red corpuscles only 
pass out by those channels which have been previously made for 
them by the colourless corpuscles. The author found no stomata of 
any kind on the epithelium of the vessels. 
Natural History of the Diatomacece. — Dr. M. C. Cooke states in 
‘ Grevillea’ (March, 1875), that Dr. Edwards has sent him a copy of 
the chapter from the Reports of the Geological Survey on the above 
subject, which is written in a popular style for general readers, and 
extends over nearly 100 quarto pages. The sections into which it is 
divided are : 1. Introduction. 2, Movements of the Diatomacefe. 
3. Mode of growth of the Diatomaceae. 4. Reproduction of the Dia- 
tomacefe. 5. Modes of occurrence and uses to man of the Diatomacefe. 
6. The Diatomacefe and Geology. 7. Directions for collecting, pre- 
serving, and transporting specimens of Diatomacefe. 8. How to 
prepare specimens of Diatomacefe for examination and study by means 
of the microscope. This enumeration of the sections will give an 
