388 General Notes. [April 
upon itself the capacity of assimilation. Recently M. Nussbaum 
took up the problem, and, according to his account as presented 
in the Biologisches Centralblatt, the layers do not thus change 
place. There appears, indeed, an ectoderm, but this arises, not 
from an alteration of the endoderm, which has taken an external 
position by the operation of turning inside out, but by a growth 
of ectoderm from that of the basal pore and from the tentacles. 
He further maintains that ectoderm is always ectoderm, and endo- 
derm can never be modified into any other layer. In regard to 
the reproduction of lost parts described by both Baker and Trem- 
bley, as well as many later observers, Nussbaum says that both 
layers must be present in order to have the missing portions re- 
produced. 
Renal Organs of Invertebrates.—Dr. McMunn has recently 
been investigating the subject of so-called renal organs in vari- 
ous molluscs as well as in the cockroach. The method was to 
boil the suspected organ in distilled water to dissolve the uric 
acid or urates. The solution was then evaporated, extracted 
with absolute alcohol, and then the residue was boiled again in 
water, filtered, and to the filtrate acetic acid was added in excess, 
and, after some hours’ standing, crystals of uric acid and urates 
were distinguished under a one-fifth objective. Other chemical 
tests were applied and with the same results. The conclusion 
was that the so-called urinary or Malpighian tubules of insects 
and the nephridia of Limax and Helix are in reality urinary in 
function, as has been heretofore believed. 
Migration of Frogs.—A peculiar migration of frogs takes 
place in the valley of the Red River of the North. The water 
of this river is green, like that of the Great Lakes, and the bot- 
tom is composed of soft clay several feet thick, which the frost 
never penetrates. To the west of the river, in Dakota, are nu- 
en y migrates to the sloughs, returning ex masse in the 
fall. I used to regard the exaggerated newspaper accounts of 
these migrations as fictions; but last autumn, in Fargo, I saw 
_ Brazilian Reptilia —Professor E. D. Cope recently read a 
paper on a collection made by Mr. H. H. Smith near Cuyaba, 
in the southern interior of Brazil. He derived from it a good 
many interesting results, especially to the knowledge of Geo- 
