598 = The Vertebrates and Invertebrates. [ October, 
Such has been the progress of zodlogy in the United States 
within less than a century. Its future progress will in part de- 
pend on the attention paid to it by medical students, to whom 
we may look for treatises on histology and embryology. At 
present there are no histologists in the United States who have 
published special monographs. When professorships of zoölogy 
alone are established in our colleges (at present mineralogy, 
botany, zoölogy, and geology are often taught by a single per- 
son) competent science-teachers will arise for our higher schools, 
and the science, we may hope, will be cultivated with something 
of the thoroughness of the German methods. At present we are 
not so greatly behind France and England as we were twenty 
years ago. There is, however, danger that Russia will outstrip 
us, and we are about on a level with the Scandinavians and the 
Dutch. 
With our energy and native ability, and the aid of well- 
endowed colleges and museums, we may hope hereafter to com- 
pete even with Germany. The development of any branch of 
science is largely dependent on individual students, and every 0p- 
portunity should be afforded young men of promise of devoting 
their time to original research. Specialists are sadly wanted m 
a country like ours, where the tendency is, perhaps, rather to the 
production of mediocrity than of genius. 
THE MISSING LINK BETWEEN THE VERTEBRATES 
AND INVERTEBRATES. 
Pa views which Dr. Dohrn has recently put forth, as to the 
details of the steps by which the vertebrate stock arose out 
of an ancestry not very much unlike the existing Annelids, are 
of such interest that, notwithstanding previous reference to the 
subject, no apology is needed for presenting the readers of 
Nature with a condensation of the main argument contained m 
The Origin of Vertebrata. 
Dr. Dohrn first draws attention to the correspondences be- 
tween vertebrate and insect embryos, which have been too little 
regarded in consequence of our designating the nervous side 1m 
the one as dorsal, in the other as ventral. Yet the facts that, 1 
both, the nervous system is developed on the convex side of y 
embryo and acquires a strong convex flexure anteriorly, and t 
. Der Ursprung der Wirbelthiere und das Princip des Functionwechsels : Ber 
logische Skizzen. Von Anton Dohrn. (Leipzig: Engelmann.) 
