Embryology. 547 
that a majority, and perhaps all, use the tube only as a winter resort, 
or for a retreat in the summer during the time of molting, though 
the testimony upon this point is by no means universal. There 
seems good reason, however, for believing that very nearly all desert 
their tubes during the spring and summer, at times, and wander in 
search of their prey. Indeed, there are indications that there are 
latitudinal, as well as seasonal variations in the habits of the family, 
i.e. that in northern latitudes proportionately a greater number 
make no tubes than in southern latitudes. The latitudinal variation 
might be called generic, in that many species of the genus in north- 
ern latitudes hide away under stones, etc., making no tubes at all ; 
while in southern latitudes many other species of the same genus 
construct tubes, some few using them habitually; many others 
temporarily. On the other hand, the seasonal variation might be 
called specific, in that most species, in any latitude, which construct 
tubes use them only during inclement seasons, or during periods of 
weakness. One species I have observed here, Lycosa fatifera 
Hentz, habitually uses its tube at all seasons; never, or very rarely, 
wandering in search of prey. I have many times watched them 
resting at the opening of the tube, waiting for passing insects. 
They will dart back into their tubes when alarmed. Hentz 
reported this species from Massachusetts and Alabama. 
have made special investigations upon the species in North Caro- 
lina, with a view to establish, if possible, the identity of Hentz’s 
Species fatifera, and the correctness of his statement that it uses the 
tube habitually at all seasons. The species can be easily recog- 
nized from Hentz’s description. The one I find here is the piceous 
variety, which Hentz reported from Alabama, and not the typical 
>i from Massachusetts.— Geo. F. Atkinson, University of North 
rolina. . 
Li 
i Y 
EMBRYOLOGY. 
THE SEVERAL FUNCTIONS OF THE ENAMEL ORGAN IN THE 
DEVELOPMENT OF THE TEETH OF MAMMALS AND ON THE IN- 
HERITANCE OF MurILATIoNs.— As long ago as 1880 Dr. A. Von 
Brunn? called attention to the fact that the cross crests of the crowns 
of the molars of the common grey rat were not completely covered 
Mey an enamel coating before eruption. The figures then pub- 
ished by Von Brunn showed that the membrana adamantina of 
the enamel organ possessed the characteristic columnar structure 
, Edited by Prof. Jno. A. Ryder, Univ. of Penna,, Philadelphia. _ 
nen tiz über un vollkommene. Schmelzentwickelung auf den Mahlzäh- 
pi eenatte Mus decumanus. Arch. f. mik. Anat. XVII., pp. 241-243, 
