SUMMARY OF CURRENT RESEARCHES 
RELATING TO 
ZOOLOGY AND BOTANY 
(principally inyertebrata and cryptogamia), 
MICROSCOPY, Etc.* 
ZOOLOGY. 
VERTEBRATA. 
a. Embryology.! 
Inversion of Germinal Layers in Mammals. — Prof. Hubrecht + 
briefly criticises Prof. Selenka’s § statement that inversion occurs in 
apes, in a degree at all comparable to that seen in Cavia , Sorex, and 
Pteropus. The condition figured by Selenka is due to the fact that in 
the apes the amnion is completed early, and the germinal disc and 
umbilical vesicle are suspended to the outer blastocyst wall by a double 
sheet of ectoderm and somatic mesoblast. If this be inversion, then 
the term must be applied to all Sauropsida and Mammals at the stage 
when the stalk of the amnion is constricted off. In a postscript to his 
paper Hubrecht considers Selenka’s revised definition, and liis view 
that germinal inversion is to be explained on mechanical grounds, as 
the result of want of space, which forces the embryonic ectoderm, plus 
the ectodermic part of the amnion, to sink inwards. Hubrecht advances 
three arguments 'against this position. In the first place, such an 
insinking of embryonic ectoderm occurs in Tupciia, while the blastocyst 
lies as free in the cavity of the uterus as does the unfolded blastocyst 
of the rabbit. Secondly, in the hedgehog the blastocyst early becomes 
fixed to the wall of the uterus, and is limited on all sides, but yet dis- 
plays no “ inversion ” worthy of the name. Thirdly, in Sorex , where 
inversion is so distinct, this does not occur until after the uterus has 
become so much inflated that there can be no lack of space. He believes 
further that the origin of the amnion from folds, which is typical for 
the oviparous Amniota, is not primitive for Mammals, and that the cases 
of inversion found in Rodents, Bats, and Primates are not cienogenetic 
phenomena, but are palingenetic. 
* 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. 
f This section includes not only papers relating to Embryology properly so called, 
but also those dealing with Evolution, Development and Reproduction, and allied 
subjects. 
X Biol. Centralbl., xix. (1899) pp. 171-5. 
§ Of. this Journal, ante, p. 17. 
