Cycladidae.-One siphon or two free siphons with simple orifices; pallial line simple; hermaphrodite, embryos incubated in external gill-plate; freshwater, Cyclas; British.
In 1865 a male of the same species was introduced, but though a strong disposition to breed was shown on the part of both, and the eggs, after the custom of the Ratitae, were incubated by him, no progeny was hatched (Proceedings, 1868, P. 329).
Since then (1904) Miss Florence Durham has shown that if the skins of young or embryonic mammals (rats, rabbits and guinea-pigs) be ground up and extracted in water, and the expressed juice be then incubated with solid tyrosin for twentyfour hours, with the addition of a very small amount of ferrous sulphate to act as an activator, a pigmentary substance is thrown down.
Nord-Ost-Afrikas, p. 1138) found that it had from two to four young or much incubated eggs.
The plate was then incubated, and, as the figure shows, the bacteria on the C-shaped area were all killed, whereas they developed elsewhere on the plate (traces of the B are just visible to the right) and covered it with an opaque growth.
The mixture is placed in a thin capillary tube and incubated at 37° C. for half an hour; a film preparation is then made from it on a glass slide, stained by a suitable method and then examined microscopically.