SUMMARY OF CURRENT RESEARCHES 
RELATING TO 
ZOOLOGY AND BOTANY 
(principally invertebrata and cryptogamia), 
MICROSCOPY, Etc. 
Including Original Communications from Fellows and Others .* * * § 
ZOOLOGY. 
VERTEBRATA. 
a. Embryology.! 
Influence of Temperature on Development.^: — Prof. 0. Iiertwig 
has made a beautiful series of experiments showing that the rate of 
development of frogs’ eggs is within limits (15°-24 0 ), a function of the 
temperature. Above the upper limit monstrosities result ; below the 
lower limit growth ceases. By means of curves the parallelism between 
“ the developmental work ” (cell-divisions, &c.) and the temperature is 
very clearly shown. It seems likely that this correlation depends in 
part on the influence of temperature on chemical reactions concerned 
with the production of nuclein and the like, increased warmth promoting 
their more rapid occurrence, lowered temperature having the opposite 
effect. But Iiertwig does not believe that this is by any means the 
only, though it may be tho most important, influence of alterations in 
temperature. 
Birth-Period of Trichosurus vulpecula.§ — Dr. J. Beard describes 
the uterine embryo and newly-born young of this marsupial, and finds 
that the “critical phase” must begin immediately before birth takes 
place, and must end soon after the animal is born, with the initiation of 
mammary nutrition. The critical and birth-periods coincide. 
He gives a fuller definition of the critical period than in his previous 
papers. “ The critical period in a morphological sense is that epoch 
of the development when all parts of the organism are first present 
as the foundations or Anlagen of all the organs ; it is that state when 
epigenesis is ended, and evolution or unfolding is beginning; it is that 
* The Society are not intended to be denoted by the editorial “we,” and they do 
not hold themselves responsible for the views of the authors of the papers noted, 
nor for any claim to novelty or otherwise made by them. The object of this part of 
the Journal is to present a summary of the papers as actually published , and to 
describe and illustrate Instruments, Apparatus, &c., which are either new or have 
not been previously described in this country. 
t This section includes not only papers relating to Embryology properly so called, 
but also those dealing with Evolution, Development, and Keproduction, and allied 
subjects. X Arch. Mikr. Anat., li. (1898) pp. 319-81 (2 pis. and 36 figs.). 
§ Zool. Jahrb. (Abth. Anat.), xi. (1897) pp. 77-96 (1 pi.). 
