ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
415 
Dreyer refers to two analogous cases, the calcification within fossil 
Echinoderms and the encrusting of sponge spicules with lime. (7) In- 
teresting sphaerocrystals of what appeared to be cellulose were also 
obtained from the solution. (8) The carapace of the crayfish also 
showed a clear webwork. 
Blitschli points out that it is no longer warrantable to infer from 
the complex structure of cellulose or chitinous membranes that these 
have arisen by direct chemical modification of corresponding structure 
in the plasma. It seems more likely that the plasma produces the 
membrane-making substances in the form of solution which coagulates 
or is precipitated superficially, there assuming in contact with the 
medium the webbed structure which he has described. Dr. Dreyer 
points out in a clear way the far reaching importance of Biitschli’s 
work. 
y. General. 
What is a Tendency ? * — Mr. A. W. Bennett submits to critical 
examination the question which forms the heading of his essay. It will 
be remembered by those who have followed recent discussions on the 
inheritance of acquired characters that much use was made of the terms 
tendency and predisposition. Mr. Bennett has failed to find an exact 
definition of these terms, and urges that if they are used vaguely and 
without any definite meaning they have no more value than the essences 
and humours of medieval naturalists. The chief object of his remarks 
is to show, that accepting Weismann’s own definition of acquired charac- 
ters, there is still in these characters an hereditable factor which renders 
it impossible to draw any satisfactory distinction between them and non- 
acquired characters. 
Action of Light on Animal Life.f — Mrs. G. C. Frankland draws 
attention to some recent experiments of Dr. Masella with guinea-pigs 
inoculated with cholera and typhoid bacilli respectively. Investigation 
was directed as to the effects of insolation previous to inoculation, and 
the effect of insolation on the animal after infection. In the case of 
both cholera and typhoid it was found that previous exposure to sun- 
shine increased the animal’s susceptibility to these diseases. When the 
exposure to sunshine took place after infection fatal results were greatly 
accelerated, for instead of dying in from 15 to 24 hours, they succumbed 
in from 3 to 5. Dr. Masella does not attempt to give any explanation 
of the remarkable results he has obtained, but Mrs. Frankland suggests 
that the action of sunshine should be tried on anti-toxines. It would 
be of great interest to ascertain how the potency of these protective 
fluids outside the body is affected by exposure to sunshine, and also of 
the result, if any, insolation had on their generation within the animal’s 
system. Dr. Masella would have us believe that his investigations 
explain the greater prevalence and virulence of typhoid and cholera in 
hot countries where the sun shines with greater power and more con- 
tinuously. Mrs. Frankland, with a dry humour, suggests that the 
London water companies may congratulate themselves that these two 
water-borne diseases maybe made to yield not only to efficient purifying 
processes at their hands, but that they have an unexpected ally in the 
limited amount of sunshine which Londoners enjoy. 
* Science Progress, iii. (1895) pp. 143-6. f Nature, lii. (1895) pp. 86 and 7. 
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