400 NATURAL SCIENCE. May. 1893. 



abnormal activity — which is inflammation — can be supposed to continue for months 

 or years. Nor does it seem to me probable that an increased rate of production of 

 the leucocytes within the body could be rendered permanent by the temporary 

 action of the attenuated virus ; for it is to be remembered that the immunity is 

 supposed to extend over certain prolonged intervals — nine months in splenic fever, 

 according to Pasteur, and seven years for the small-pox, according to the medical 

 faculty ; and if protective inoculation merely consists in the increase in the strength 

 and activity of the standing army of leucocytes, then fue inoculation should suffice 

 for all diseases ; he who is protected by inoculation with the cholera virus should be 

 proof against small-pox, and the virus of scarlet fever should protect against typhus. 

 Moreover, might not such a state of leucocytal activity be produced by other means, 

 without the introduction of microbes or poison from a diseased animal — an idea 

 which, to say the least, is lacking in poetry ? That such were the case is, indeed, 

 a " consummation devoutly to be wished " and prayed for. If Dr. Hurst can prove 

 his proposition he will have the thanks of a long-suffering public, threatened with 

 the nightmare anticipations of a life spent in being inoculated — a veritable flying 

 from " the ills we have to others that we know not of." 



Finally, I must remind Dr. Hurst that the inoculation liquids of many experi- 

 menters contain no microbes. Dr. Koch's consumption vaccine, I believe, contained 

 none, nor does that of Dr. Kraftkine 



G. W. BULMAN. 



"Twins and Triplets" in Doris. 



Mr. J. Arthur Thomson refers to the frequency of "twins and triplets" in 

 Doris, meaning thereby two or more embryos developing within a single egg, and 

 suggests that it may be due to " the fact that the ribbons [of eggs] are battered to 

 and fro by the surge." 



I have observed the same phenomenon, however, in eggs laid by a Doris in an 

 aquarium, and not exposed to any movement at all. 



April 15, 1893. C. Herbert Hurst. 



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ERRATA. 



P. 254, line 21, for " Caprettx " read "Caprellae." 



P. 255, line 13 from bottom, for " Hasting " read " Harting. 



P. 259, the block was lent by Dr. Sclater. 



