NOTES AND MEMOBANDA. 79 



and settles permanently. The middle segment then protrudes on each 

 side of the head segment, and gradually encloses it, thus producing 

 the dorsal and ventral shell so characteristic of the entire class. This 

 unlooked for, simple development could not have been predicated by 

 any study of the adult animal, but remarkably sustains the homologies 

 insisted upon two years ago by Professor Morse in his papers upon 

 the subject. 



A supposed New Potato Disease. — A paragraph has appeared in 

 several scientific papers, quoted from the ' Zeitschi'ift fiir Parasiten- 

 kimde,' stating thai; Professor Hallier of Jena has described a new 

 potato disease, which made its appearance last autumn in the neigh- 

 bourhood of that town, the disease being indicated by the presence of 

 a purple web, and the appearance of a number of black spots on the 

 skin, referable apparently to the perithecia of a pyrenomycetous fungus. 

 We learn, says ' Nature,' from the Eev. M. J. Berkeley, that this so- 

 called new disease is nothing but the well-known " copper-web," which 

 is in some years very destructive to asparagus, mint, and other crops, 

 and has been known in some instances to attack the potato. The de- 

 scription in the ' Zeitschrift ' is identical with this familiar parasite. 

 Figures will be found in Tulasne's ' Fungi Hypogfei,' under Ehizoc- 

 tonia, showing that the so-called perithecia are spurious. Mr. Broome 

 has detected the form of fructification known as Conidia. 



NOTES AND MEMORANDA. 



An Immersion Tube for the Microscope. — The arrangement that 

 was exhibited at the last meeting, by Mr. E. Eichards, F.E.M.S., 

 consists of a tube having the universal screw at each end, over which 

 the inunersion tube is fitted with a cap, after the principle of the pro- 

 tecting cap which the inventor brought before the notice of the Society 

 in June, 1872. It will admit of immersing the tube deep enough to 

 bring objects into view in about eight or ten inches of water; the 

 powers most useful are from four inches to one inch. The mode of 

 using this accessory is merely to screw one end of the inner tube to 

 the microscope body, and screw the object-glass into the other end, 

 after which put on the immersion tube, the position of which must be 

 regulated according to the power intending to be used. It can be used 

 with any microscope which has an aperture in the stage large enough 

 to admit the tube passing through, or where the stage can be re- 

 moved. 



Professor Betz's mode of preparing Sections of the Brain. — 



This is given very fully in Dr. Batty Tuke's 'Journal of Mental 

 Science.' It is stated that the Professor has lately produced brain- 

 sections which have attracted very considerable attention in Vienna. 

 His specimens are of vast extent. He appears to be able to produce 

 thin sections of an entire hemisphere. Dr. Tuke gives his method 

 of hardening and cutting as it is stated in the ' Correspondez Blatt 



