376 
NOTES AND MEMORANDA. 
anthracis) is artificially cultivated in an indifierent fluid, 
by the method of successive generations, which I have 
described in my report, each successive generation becomes 
less active than its predecessor, and when inoculated acts 
not only with less intensity, but more gradually, and often 
in a somewhat difierent manner. This modification takes 
place to such a degree that w^hen the cultivation has been 
carried to the fourteenth or fifteenth generation, it may 
be introduced with impunity into the system of a mouse, 
which is one of the animals most susceptible to the poison. 
Apart from its scientific interest, this fact will doubtless 
prove to be of practical value, for by its means it will be 
possible to obtain a virus of sufficient activity to produce an 
attack of the disease which shall be protective, but not of 
sufficient severity to be dangerous, or in any way injurious 
to the animal inoculated. 
With regard to any apprehended ill-effect upon the 
animals thus inoculated, I may say that the cows which we 
have used have thriven remarkably well, and none so well 
as that which has been most severely tested. 
I hope in a future report to give the details of these in- 
vestigations, which have necessarily been extensive and 
complicated. 
I venture, therefore, to urge upon the Society the im- 
portance of continuing these experiments, so as to bring 
them to a complete and decisive result. In order to do this, 
further outlay in the purchase and keep of animals, and 
other expenses, will be necessary, which will involve the 
renewal of the grant for the ensuing six months. 
Dr. Carl Rabl on the Pedicle of Invagination in Pulmonate 
Gastropoda. — Dr. Rabl has renewed his investigations on the 
embryology of Planorbis, and has arrived at a result which 
brings his observations of fact and my own (published in 
this journal in 1874) into close agreement on a matter of 
considerable importance concerning which he was at first led 
to differ from me. 
He writes relatively to the question of the existence of a 
pedicle of invagination^’ as follows (dated June 4th) : 
The youngest embryos, of which I have cut sections in 
order to determine the above question, were little older than 
those drawn by me in Plate XXXII, fig. 20, of my Memoir. 
Although by observation of the embryos as whole objects 
I could see nothing which could lead to the inference of the 
existence of a pedicle of invagination, yet I convinced my- 
self by the aid of sections that a cylindrical solid cord 
