[March, 
160 Analyses of Boohs . 
eluding all degrees below that of human and animal conscious- 
ness, as well as all degrees above it.” He holds, therefore, that 
mind runs deeper down into matter than is generally supposed. 
Having identified force with consciousness, he asks if we have 
still an irreconcilable duality ? In reply he maintains that con- 
sciousness is an ultimate faCt which cannot be surrendered, — 
that matter is that something whose modifications are states of 
consciousness. “ In the aCt of atomic collision matter and con- 
sciousness, the thing modified and its modification, are causally 
and efficiently related. Hence matter and consciousness are in 
their ultimates the same, and consciousness is the ultimate, 
unitary cosmic constituent. 
We regret that space does not enable us to develop the author’s 
argument at length. 
John Hopkins University , Baltimore. Studies from the Biolo- 
gical Laboratory . “ The Development of the Oyster,” by 
W. K. Brooks, Associate in Biology. No. IV. Baltimore : 
J. Murphy and Co. 
We have here a very valuable monograph. The author finds, in 
the first place, that, as regards the American oyster of the 
Chesapeake Bay, the ova are fertilised not within, but without, 
the body of the parent — an important difference from the 
European species. After describing the general anatomical cha- 
racters of the species, he passes to an account of his experiments 
on the artificial fecundation of the ova. In connection with this 
subjeCt he finds that the American oyster, like its European con- 
gener, is not a hermaphrodite ; but he states that there is some 
reason for the belief that an oyster may produce eggs one season 
and sperm-cells the next. 
The author has very carefully studied the development of the 
young brood, and it is to be especially noted that he finds them 
pass through a distinCtly-marked “ gastrula ” stage. Mr. Brooks 
has unfortunately failed in tracing the process by which the 
swimming embryo becomes converted into the sedentary adult. 
The chance of a young oyster reaching maturity has been calcu- 
lated by Mobius at i in 1,145,000. 
The author remarks that the general occurrence of a gastrula 
stage in so many widely separated animals is certainly the most 
pronounced feature in embryology, and it is possible that a more 
complete acquaintance with the development and the phylogeny 
of the Mollusca may show that the faCts held do not in reality 
oppose the view that it is an ancestral form. But our knowledge 
of faCts, he adds, must be very much greater before we are 
