306 NOTES AND MEMORANDA. 
exhaustively of the subject of the structure of the connective tissue. 
The author deals principally with molluscan structures, giving those 
of Mytillus edulis and Anodonta piscinalis very fully. He makes out 
connective tissue to be a far more complex structure than it is gene- 
rally believed to be, and his preparations, which are capitally drawn, 
bear him out. The preparations have been mounted in various ways. 
He has used, for example, alcohol, bichromate of potass, turpentine, 
glycerine, and osmium. For injections he has used Prussian blue and 
picro-carmine. The most important point he shows is that of the 
relation of the so-called schleim-cells. The memoir covers fifty pages. 
—There is also a short paper, by Herr Fr. Meyer, on preservative 
fluids for microscopic objects. 
Reichert and Du Bois-Reymond’s Archiv (January).—Carl Sachs 
describes and figures the terminations of nerve-fibres in certain ten- 
dons.—F. Boll’s article on the Savian vesicles found in the torpedo 
about the nasal orifices and between the external edges of the elec- 
trical organs and the limb-cartilages, is very interesting, because he 
demonstrates the existence in their epithelium of spindle-shaped cells 
corresponding in character to those so commonly found in special 
sense organs. 
The Zeitschrift fiir Wissenschaftliche Zoologie, vol. xxvi. part 2.—In 
this Herr Repiachoff continues his contributions on the Chilostomous 
Bryozoa, giving many interesting particulars about the development 
of the amphiblastic ovum of Lepralia and Tendra.—Herr Ludwig Graff 
describes the anatomy of the Sipunculoid Chetoderma nitidulum.— 
Dr. Hubert Ludwig writes on the interesting Gastrotrichous Rotifers, 
established as a separate order by Metschnikoff. 
NOTES AND MEMORANDA. 
Is Vision with the Microscope Finite or Unlimited 2—A paper on 
this subject appears in the ‘ Boston Journal of Chemistry, and is 
evidently written by one who is accustomed to microscopical re- 
search. We give it in full as follows:—The question of the limits 
of visibility is an eminently practical one, of great interest to all 
microscopists and physicists. On this question Mr. Sorby says: “ The 
highest powers of our best modern microscopes, he {Helmholtz ?] 
assumes, will enable us to see objects an eighty-thousandth part of an 
inch in diameter.” This sentence hardly represents Mr. Sorby’s posi- 
tion. After referring to Helmholtz’s principles of interference fringes, 
or diffraction, he says, “ It appears to me that we cannot do better than 
to adopt these principles in forming some conclusion as to the size of 
the smallest object that could be seen with a theoretically perfect 
microscope. Looked at from this point of view alone, with a dry 
lens this could not be less than one 80,000th of an inch.” This 
