510 Recent Literature. [July, 
is to bring out at least much more clearly than has before been 
done, the fact that between the crystalline and the oldest primor- 
dial rocks, “there is a great chronologic break, a ‘lost interval’ of 
immense duration,” and also that the geological formations are 
oldest on the sea-board, becoming successively newer as we pro- 
ceed from Massachusetts bay to the Berkshire hills in the west- 
ern part of the State. Bearing these two points in mind, the 
volume will be read with much interest, afford food for further 
discussion, and doubtless will lead local geologists to a more 
careful study of their neighborhood. The region here treated of 
is most difficult to study and understand; a flood of light has 
been thrown upon the subject by Mr. Crosby, and many facts 
which will be of constant use in future discussions are here re- 
corded. The map especially is an excellent graphic résumé of 
the subject. It is not often the case that a city society does so 
much as the one at Boston to promote the study of local geology, 
in this respect it has set a most useful example to similar organi- 
zations. 
Brooks’s DEVELOPMENT OF THE OysTER.!—Thisis the first attempt 
pletely, the shell appearing at the point which the blastopore 
previously occupied, while directly opposite the position of the - 
blastopore, the mouth and then the anus of the digestive tract 
make their appearance. The Veliger has the general form of that 
of Cardium and other Lamellibranchs. 
Dr. Brooks thinks that the embryology of the oyster bears out 
his view that Lamellibranchs must be regarded as a side branch 
from the main molluscan stem, of which the Gasteropods are a much 
more direct continuation, “ and that all attempts to trace the phy- 
logeny of the higher Mollusca through the Lamellibranchs to 
1 Johns Hopkins University, Baltimore. Studies from the Biological Laboratory, 
The Development of the Oyster. By W.: K. Brooks. No tv. Baltimore, 1880. 8vo. 
pp- 84. 11 plates. 
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