Marcu 15, 1901.] 
imagine the opossums to have originally gained 
access to the region, is it not preeminently fit- 
ting that, in establishing the foundation of an 
extremely comprehensive adaptive radiation, 
and under the favorable conditions of an abso- 
lute freedom from competition, they should 
have thrown aside their original didelphyid 
characters? And especially is this conceivable 
when we realize that the differences of structure 
separating the opossums from the most primitive 
of the Australian forms (dasyures) are ex- 
tremely slight. 
However uuprogressive the opossums may at 
first sight appear to be, they are still plastic 
types. That they are at the present time at- 
tempting to radiate in South America is ap- 
parent from the numerous subgeneric divisions 
which it has been found necessary to establish, * 
and more especially from the fact that one form 
(Chironectes) has already become completely 
adapted to an aquatic life. 
The above conception approximates closely 
the general opinion, expressed by Lydekker, ¢ 
in 1896, that the opossums and dasyures are 
the descendants of a common ancestral stock, 
but differs in assuming that these ancestors 
were opossums, and that they were formerly 
present in Australia. If we assign to the ances- 
tors of the dasyures characters which would 
allow them to constitute the Marsupial proto- 
type, they would no longer be Dasyures, but 
opossums. Ameghino has suggested the South 
American Microbiotheriide as ancestral to the 
dasyures, and Bernard (Eléments de paléon- 
tologie) regards the border as opossums. 
B. ARTHUR BENSLEY. 
COLUMBIA UNIVERSITY, 
November 5, 1900. 
WORK AT THE MARINE BIOLOGICAL LABORA- 
TORY OF WOOD’S HOLL, 1900. 
THE course in physiology should be classified 
as a kind of research. Thesame is true in large 
measure of the course in embryology. In both 
*Cf. Thomas, O., ‘ British Museum Catalogue of 
Marsupialia and Monotremata,’ London, 1888, pp. 
317-322. 
7 Cf. Gadow, H., ‘On the systematic position of 
Notoryctes typhlops, BP. Z. S.,’ London, 1892, p. 370. 
{ Lydekker, R., ‘A Geographic History Mammals,’ 
Cambridge, 1896, p, 55. : 
SCLENCE. 
433 
of these courses, for instance, Dr. Loeb’s ex- 
periments on artificial parthenogenesis were 
successfully repeated. Both of these courses 
are attracting students from medical colleges 
who feel the need of getting away from the 
strictly conventional physiology and embry- 
ology, into touch with the new lines opening 
up—in physiology, with the comparative study 
of biokinetics and in embryology with the new 
lines of thought introduced by experimental 
work and by the studies in cell-lineage. Both 
of these courses, as given here, are largely the 
outcome of the results of research of preceding 
years by members of the laboratory, who are 
themselves concerned in giving the instruction. 
They therefore represent the spirit of the labora- 
tory along these two lines of investigation. 
As regardsinvestigation proper :—In PHYSI- 
oLoey, Dr. Loeb has continued his experiments 
on artificial parthenogenesis and has succeeded 
in inducing the development of unfertilized eggs 
of Annelids (see a recent number of ScIENcE). 
Other lines of work in physiology concern the 
chemical stimulation of nerves, the physiolog- 
ical effects of inorganic salts on the rhythmical 
activity of living tissues, similar studies on 
ciliary motion ; and work on regeneration by 
several investigators. 
In CyToLoGy : work on spermatogenesis has 
been carried on by Dr. Montgomery, Mr. Down- 
ing and Miss Wallace; on ovogenesis by Mr. 
Arthur E. Hunt, Dr. H. BE. Crampton and Dr. 
C. M. Clapp; on fertilization by Dr. Conklin, 
Miss Katharine Foot, Miss Strobell, Dr. F. R. 
Lillie, Mr. Martin Smallwood. Dr. E. B. Wil 
son has brought here his experimental work on 
fertilization and cleavage in the sea urchin eggs. 
In EMBRYOLOGY work has been carried on in 
various lines: Annelids by Dr. A. C. Treadwell 
and Mr. R. S. Lillie, parasitic copepods by Mr. 
Edward Rynearson, Cirripedia by Mr. M. A. 
Bigelow, fishes by Dr. Cornelia M. Clapp, Miss 
Robinson, Dr. Neal and Miss A. C. Smith, 
Monotremata by Mr. B. A. Bensley, Histogenesis 
of gastric glands of Amphibia by Dr. R. R. Bens- 
ley, Planaria by Mr. W. C. Curtis, Nucula by 
G. A. Drew, Parasitic Isopods by J. R. Murlin. 
The work in NEUROLOGY included the fol- 
lowing: V. E. MéCaskill on nervous sys- 
tem and metamerism of Hirudo, Mr. Fling 
