690 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
SUMMARY 
OF CURRENT RESEARCHES RELATING TO 
ZOOLOGY AND BOTANY 
(principally Invertebrata and Cryptogamia'), 
MICROSCOPY, &c., 
INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.* 
ZOOLOGY. 
A. VERTEBRATA Embryology, Histology, and General. 
a. Embryology, f 
Intensive Segregation.^ — Lev. J. T. Gulick advances from the 
position maintained in a previous paper on “ Divergent Evolution 
through Cumulative Segregation.” There he enumerated no less than 
eighteen sets of natural causes dividing species into sections which do 
not interbreed, and sought to show how these causes, often acting in 
complex combination, tend to produce cumulative segregation and di- 
vergent evolution. His object now is to show how separation from the 
first involves more or less segregation, or how segregation, that at first 
divides the species into sections with reference to some one endowment, 
is always tending toward intensified segregation in which the sections 
present differences in regard to an increasing number of endowments. 
Experience in domestication shows that segregation is a controlling 
factor, whether it be in the deliberate preservation of special varieties, 
or simply in that prevention of crossing which necessarily results when 
separate sections of a domesticated species are under the care of distinct 
tribes of men. But in nature species are similarly divided into sections, 
which are usually assorted with reference to some definite point or points 
of character, and divergent evolution results. Division of the species 
involves some segregation, and whenever the transforming influences of 
the other factors of evolution begin to operate in the different sections, 
the initial segregation is inevitably intensified and the divergence in- 
creased. For it is in the last degree improbable that change produced 
* 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 Reproduction, and allied 
subjects. X Journ. Linn. Soc. Lond.— Zool., xxiii. (1890) pp. 312-80. 
